Search

This paper reports the extraction and separation of no-carrier-added (NCA) 195,195m,197mHg radioisotopes produced in 20 MeV 1H irradiated Au target. The extraction studies were carried out from HNO3 media by solid–liquid extraction using TK200 and DGA-N resins based on trioctylphosphine oxide (TOPO) and N,N,N,N-tetra-n-octyldiglycolamide (TODGA) respectively. TK200 resin was found to be the superior extractant for separation of NCA Hg radionuclides from 3 M HNO3 with a separation factor of 3.2 × 105.

Separation of Pb and Bi from a 20 MeV 1H irradiated lead–bismuth eutectic (LBE) target has been carried out using DGA-N and TK-200 resins based on N,N,N,N-tetra-n-octyldiglycolamide (TODGA) and trioctylphosphine oxide (TOPO) respectively. The sorption studies were carried out under different acidic conditions and monitored by the radiotracers 206Bi and 203Pb using a gamma spectrometric technique. Both resins could extract Bi from the nitric acid medium but the selectivity of the TK-200 towards Bi is higher. At pH 4, TK-200 extracts Bi from LBE solution with a high separation factor, in the order of 106.

Decay of 244Am m,g , produced by neutron irradiation of 243Am, has been studied by singles and coincidence measurements of decay γ rays. Two new γ rays of energy 940.54 ± 0.08 and 983.46 ± 0.08 keV have been observed in the decay of 244Am m which suggests a new level of 983.5 keV in 244Cm. This level has been assigned a tentative spin of (1 − ). In the present studies, uncertainties in the γ -ray intensities of 244Am m,g have been significantly reduced by nearly an order of magnitude for most of the γ rays. The data of half-lives have also been improved. More precise half-lives for 244Am m ( T 1∕2 = 26 .13 ± 0.43 min) and 244Am g ( T 1∕2 = 600 .4 ± 1.8 min) have been obtained.

Kinetic-energy spectra and angular distributions of the projectile-like fragments were measured in $^{12,13}\mathrm{C}+^{93}\mathrm{Nb}$ reactions at ${E}_{\mathrm{lab}}=65\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ to investigate the reaction mechanisms involving the role of projectile and target structures. It has been observed that one-nucleon pick-up reactions lead to the formation of target-like fragments predominantly in the ground state, whereas nucleon transfer to the target occurs predominantly in the excited states for both $^{12}\mathrm{C}+^{93}\mathrm{Nb}$ and $^{13}\mathrm{C}+^{93}\mathrm{Nb}$ reactions. In the case of $^{93}\mathrm{Nb}(^{12}\mathrm{C}, ^{15}\mathrm{N})^{90}\mathrm{Zr}$ reactions, a significant yield was observed for $^{15}\mathrm{N}$ (``$1p+2n$'' pick-up) indicating the role of the $N=50$ shell in $^{90}\mathrm{Zr}$. Observation of a systematic increase in the forward peaking of the angular distributions of projectile-like fragments with an increasing number of nucleon transfers indicates an increase in the projectile-target overlap with increasing mass transfer. Angular distributions for inelastic scattering as well as transfer channels populating various states of projectile-like fragments and/or target-like fragments were calculated simultaneously by using the coupled reaction channels code fresco and were in reasonable agreement with the experimental data. New (modified) spectroscopic amplitudes have been proposed for some of the unknown (known) overlapping states for calculating transfer cross sections. In the case of $^{13}\mathrm{C}+^{93}\mathrm{Nb}$, the transfer channels corresponding to ``$2n$'' and ``$1p+1n$'' pick-up channels were not observed. This may be due to the higher N/Z ratio of the projectile, highlighting the importance of projectile structure in addition to that of the target.

Mass distribution of fission products has been determined in $$\upalpha +^{\mathrm {232}}\hbox {Th}$$ reaction at $$E_{\mathrm {lab}}=36.2$$ MeV using $$\upalpha $$ particles from the cyclotron at the Variable Energy Cyclotron Centre (VECC), Kolkata. Yields of 64 fission products having half-lives in the range of about $$\sim 1$$ min to several days have been measured using gamma ray spectrometry. The mass distribution shows a clear triple humped structure indicating the contribution from both asymmetric and symmetric modes of fission. The experimental mass distribution was well reproduced by the calculation from the GEF code, which takes into account the multi-chance fission.

Fission fragment mass distribution has been measured for $^{28}\mathrm{Si}+^{197}\mathrm{Au}$ reaction at bombarding energies around the Coulomb barrier (${V}_{b}=126.5\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$). The experimental variance of the mass distribution shows a sudden change from monotonic decrease to a saturation at energies close to the Coulomb barrier and again a decreasing trend at sub-barrier energies. The variance of the mass distribution was also obtained from dynamical and statistical model calculations for the fission of a fully equilibrated compound nucleus. Both of the theoretical calculations show a monotonic change of the mass variance around the Coulomb barrier. The anomalous dependence of fission fragment mass width at energies around the barrier may be due to the dominance of the quasifission process as compared to compound nuclear fission.

In this article, some of our recent results on fission fragment /product angular distributions are discussed in the context of non-compound nucleus fission. Measurement of fission fragment angular distribution in 28Si +176Yb reaction did not show a large contribution from the non-compound nucleus fission. Data on the evaporation residue cross-sections, in addition to those on mass and angular distributions, are necessary for better understanding of the contribution from non-compound nucleus fission in the pre-actinide region. Measurement of mass-resolved angular distribution of fission products in 20Ne +232Th reaction showed an increase in angular anisotropy with decreasing asymmetry of mass division. This observation can be explained based on the contribution from pre-equilibrium fission. Results of these studies showed that the mass dependence of anisotropy may possibly be used to distinguish pre-equilibrium fission and quasifission.

Lithium titanate is a proposed tritium breeding blanket material in D-T based fusion reactor under International Thermonuclear Experimental Reactor programme. For optimization of sol–gel preparation method and chemical quality control, compositional characterization of Li2TiO3 was carried out by particle induced gamma-ray emission using 8 MeV proton beam at BARC–TIFR pelletron facility. For the first time, a non-destructive method has been standardized for simultaneous determination of Li, Ti and O in this ceramic sample, which is otherwise difficult by various wet-chemical as well as radio-analytical methods. Thick targets of samples, synthetic samples and standards prepared in graphite matrix were used for the experiment. Rutherford backscattering spectrometry method was used for beam current monitoring using a thin Au foil. The gamma-rays at 478, 983 and 6129 keV from 7Li(p, p′γ)7Li, 48Ti(p, p′γ)48Ti and 16O(p, p′γ)16O nuclear reactions, respectively, were measured using high resolution gamma-ray spectrometry and corresponding peak areas were used for concentration calculations by relative method.

Background: The angular distribution of fission fragments or products is a sensitive probe to investigate non-compound-nucleus (NCN) fission. However, the gross angular distribution cannot distinguish between different NCN fission processes. Both preequilibrium fission and quasifission contribute to NCN fission and would both result in deviations from the statistical saddle point model (SSPM). Mass-resolved angular distributions of the fission product offers the possibility to distinguish between the two mechanisms [Sodaye et al., Phys. Rev. C 95, 014612 (2017); Tripathi et al., Phys. Rev. C 88, 024603 (2013); Vorkapic and Ivanisevic, Phys. Rev. C 55, 2711 (1997)].Purpose: Mass and mass-resolved angular distributions of fission products have been measured in the $^{16}\mathrm{O}+^{238}\mathrm{U}$ reaction at ${E}_{\mathrm{lab}}=85.3\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ to investigate the dominant NCN fission mechanism at sub-barrier energy.Method: Mass and mass-resolved angular distributions were measured by recoil catcher technique followed by offline \ensuremath{\gamma}-ray spectrometry.Results: The mass distribution was observed to be predominantly asymmetric. The angular anisotropy of the fission products was observed to be independent of their mass.Conclusions: The mass independence of the angular anisotropy suggested quasifission to be the dominant NCN fission process. This was further confirmed from the underestimation of angular anisotropy by theoretical calculations even after including the contribution from preequilibrium fission.

Background: Non-compound-nucleus fission in the preactinide region has been an active area of investigation in the recent past. Based on the measurements of fission-fragment mass distributions in the fission of $^{202}\mathrm{Po}$, populated by reactions with varying entrance channel mass asymmetry, the onset of non-compound-nucleus fission was proposed to be around ${Z}_{p}{Z}_{t}\ensuremath{\sim}1000$ [Phys. Rev. C 77, 024606 (2008)], where ${Z}_{p}$ and ${Z}_{t}$ are the projectile and target proton numbers, respectively.Purpose: The present paper is aimed at the measurement of cross sections and spin distributions of evaporation residues in the $^{28}\mathrm{Si}+^{176}\mathrm{Yb}$ reaction (${Z}_{p}{Z}_{t}=980$) to investigate the fusion hindrance which, in turn, would give information about the contribution from non-compound-nucleus fission in this reaction.Method: Evaporation-residue cross sections were measured in the beam energy range of 129--166 MeV using the hybrid recoil mass analyzer (HYRA) operated in the gas-filled mode. Evaporation-residue cross sections were also measured by the recoil catcher technique followed by off-line $\ensuremath{\gamma}$-ray spectrometry at few intermediate energies. $\ensuremath{\gamma}$-ray multiplicities of evaporation residues were measured to infer about their spin distribution. The measurements were carried out using NaI(Tl) detector-based 4\ensuremath{\pi}-spin spectrometer from the Tata Institute of Fundamental Research, Mumbai, coupled to the HYRA.Results: Evaporation-residue cross sections were significantly lower compared to those calculated using the statistical model code pace2 [Phys. Rev. C 21, 230 (1980)] with the coupled-channel fusion model code ccfus [Comput. Phys. Commun. 46, 187 (1987)] at beam energies close to the entrance channel Coulomb barrier. At higher beam energies, experimental cross sections were close to those predicted by the model. Average $\ensuremath{\gamma}$-ray multiplicities or angular momentum values of evaporation residues were in agreement with the calculations of the code ccfus + pace2 within the experimental uncertainties at all the beam energies.Conclusions: Deviation of evaporation-residue cross sections from the "fusion + statistical model" predictions at beam energies close to the entrance channel Coulomb barrier indicates fusion hindrance at these beam energies which would lead to non-compound-nucleus fission. However, reasonable agreement of average angular momentum values of evaporation residues at these beam energies with those calculated using the coupled-channel fusion model with the statistical model codes ccfus + pace2 suggests that fusion suppression at beam energies close to the entrance channel Coulomb barrier where populated $l$ waves are low is not $l$ dependent.

We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

Projectile breakup cross sections in the $^{6}\mathrm{Li}+^{112}\mathrm{Sn}$ reaction have been measured at two beam energies, 30 and 22 MeV. Cross sections for sequential breakup of $^{6}\mathrm{Li}$ into $\ensuremath{\alpha}+d$ via its resonant state of ${1}^{+}$ (5.65 MeV) in the continuum have been measured for the first time along with two other dominant resonant states of ${3}^{+}$ (2.18 MeV) and ${2}^{+}$ (4.31 MeV) at ${E}_{\mathrm{beam}}=30$ MeV. However, at 22 MeV, the $\ensuremath{\alpha}+d$ breakup is found to be only due to direct breakup process. Cross sections measured for sequential breakup via two transfer channels, $(^{6}\mathrm{Li},^{5}\mathrm{Li})$ and $(^{6}\mathrm{Li},^{8}\mathrm{Be})$, into $\ensuremath{\alpha}+p$ and $\ensuremath{\alpha}+\ensuremath{\alpha}$, respectively, and the above $\ensuremath{\alpha}+d$ breakup channels compared with the results of coupled-channels calculations unravel the reaction mechanisms involving a weakly bound projectile and different processes leading to large inclusive $\ensuremath{\alpha}$-particle production.

A particle induced gamma-ray emission method using proton beam in conjunction with in situ current normalization approach was standardized for non-destructive determination of low Z element lithium and was applied for quantification of Li in lithium doped neodymium dititanate (Nd2Ti2O7) ceramic sample. Thick pellets of heat treated samples, their precursors and Li standards were prepared separately by homogeneously mixing with cellulose and fixed amount of F used for in situ current normalization. For validation of the method, four synthetic samples were also analyzed. Samples and standards were irradiated with 4 MeV proton beam (~5 nA current) from folded tandem ion accelerator (FOTIA) BARC, Mumbai. Characteristic γ-rays of 478 keV from 7Li to 197 keV from 19F were measured by high resolution γ-ray spectrometry. The Li concentrations determined in the six samples were in the range of 0.29–0.85 wt%. The Li contents in heat treated samples gave the idea about loss of Li compared to their precursors.

Barium borosilicate glass (BaBSG) is proposed as a potential candidate for vitrification of nuclear waste generated from thoria based nuclear reactors. Along with fission products, activation products and many inactive chemicals, like fluorine in the form of HF are expected to be present in the dissolver solution with nuclear waste. As vitrification occurs at high temperature, it is important to quantify fluorine in BaBSG. Due to its complex matrix, most of the wet chemical and nuclear analytical methods encounter problems in the estimation of fluorine. Particle induced γ-ray emission (PIGE) method has been standardized for non-destructive determination of fluorine contents in BaBSG samples utilizing measurement of prompt gamma-rays from 19F (p, p’γ) 19F reaction. Experiments have been carried out with thick pellet targets prepared in cellulose matrix using 4 MeV proton beam from the folded tandem ion accelerator at BARC, Mumbai. For obtaining current normalized count rate of interest, beam current variation was monitored by the Rutherford backscattering spectrometry (RBS) method as well as by the in situ approach using an externally added element sensitive to PIGE. In this paper standardization of PIGE methods for F determination, validation of methods using synthetic samples, and application to BaBSG samples are reported.

Formation cross-sections of evaporation residues have been measured in 19 F +159 Tb reaction at E lab =83, 88, 93, 98 and 103 MeV using recoil catcher technique followed by off-line gamma-ray spectrometry. Significant contribution from incomplete fusion has been observed at these low beam energies indicating the contribution to incomplete fusion from collision trajectories with angular momentum (l) less than the critical angular momentum for complete fusion (l cr (CF)) . Incomplete fusion cross-sections could be explained using a modified sum-rule model which allows effective competition from incomplete fusion for collision trajectories with l cr (CF) .

Diffusional transport properties of hydrophobic anion-exchange membranes were studied using the polymer inclusion membrane (PIM). This class of membranes is extensively used in the chemical sensor and membrane based separation processes. The samples of PIM were prepared by physical containment of the trioctylmethylammonium chloride (Aliquat-336) in the plasticized matrix of cellulose triacetate (CTA). The plasticizers 2-nitrophenyl octyl ether, dioctyl phthalate, and tris(2-ethylhexyl)phosphate having different dielectric constant and viscosity were used to vary local environment of the membrane matrix. The morphological structure of the PIM was obtained by atomic force microscopy and transmission electron microscopy (TEM). For TEM, platinum nanoparticles (Pt nps) were formed in the PIM sample. The formation of Pt nps involved in situ reduction of PtCl(6)(2-) ions with BH(4)(-) ions in the membrane matrix. Since both the species are anions, Pt nps thus formed can provide information on spatial distribution of anion-exchanging molecules (Aliquat-336) in the membrane. The glass transitions in the membrane samples were measured to study the effects of plasticizer on physical structure of the membrane. The self-diffusion coefficients (D) of the I(-) ions and water in these membranes were obtained by analyzing the experimentally measured exchange rate profiles of (131)I(-) with (nat)I(-) and tritiated water with H(2)O, respectively, between the membrane and equilibrating solution using an analytical solution of Fick's second law. The values of D(I(-)) in membrane samples with a fixed proportion of CTA, plasticizer, and Aliquat-336 were found to vary significantly depending upon the nature of the plasticizer used. The comparison of values of D with properties of the plasticizers indicated that both dielectric constant and viscosity of the plasticizer affect the self-diffusion mobility of I(-) ions in the membrane. The value of D(I(-)) in the PIM samples did not vary significantly with concentration of Aliquat-336 up to 0.5 mequiv g(-1), and thereafter D(I(-)) increased linearly with Aliquat-336 concentration in the membrane. The self-diffusion coefficients of water D(H(2)O) in PIM samples were found to be 1 order of magnitude higher than the value of D(I(-)) and varied slightly depending upon the plasticizer present in the membrane. It was observed in electrochemical impedance spectroscopic studies of the PIM samples that diffusion mobility of NO(3)(-) ions was 1.66 times higher than that of I(-) ions, and diffusion mobility of SO(4)(2-) ions was half of that for I(-) ions. The theoretical interpretation of experimental counterions exchange rate profiles in terms of the Nernst-Planck equation for interdiffusion also showed higher diffusion mobility of NO(3)(-) ions in the PIM than Cl(-), I(-), and ClO(4)(-) ions, which have comparable diffusion mobility.

Cross sections of reaction products were measured in [Formula: see text]Si[Formula: see text]Nb reaction using recoil catcher technique involving by off-line gamma-ray spectrometry at beam energies of 105 and 155[Formula: see text]MeV. At [Formula: see text][Formula: see text]MeV, the contribution from different incomplete mass transfer processes is investigated. Results of the present studies show the contribution from deep inelastic collision (DIC), massive transfer or incomplete fusion (ICF) and quasi-elastic transfer (QET). The contribution from massive transfer reactions was confirmed from the fractional yield of the reaction products in the forward catcher foil. The present results are different from those from the reactions with comparatively higher entrance channel mass asymmetry with lighter projectiles, for which dominant transfer processes are ICF and QET which involve mass transfer predominantly from projectile to target. The [Formula: see text] values of the products close to the target mass were observed to be in a wide range, starting from [Formula: see text] of the target ([Formula: see text]Nb) and extending slightly below the [Formula: see text] of the composite system, consistent with the contribution from DIC and QET reactions. At [Formula: see text][Formula: see text]MeV, a small contribution from QET was observed in addition to complete fusion.

Palm shell (Borassus Flabellifer), a ligno-cellulosic agrowaste is used as adsorbent for the removal of Hg(II). A series of experiments were conducted in a batch system to evaluate the effect of system variables. The optimal pH value of mercury(II) adsorption onto palm shell powder was found to be pH 3.0–7.0. The maximum uptake capacity was found 0.04425 mg/g. The pseudo second order rate equation was found to be the best fit for the kinetic data obtained. The equilibrium data were found to follow both Freundlich and Langmuir isotherm models with high coefficients of determination.

Functionalized membranes containing carboxylate, phosphate and sulfonate groups were prepared by UV-initiator induced graft polymerization of the functional monomer (acrylic acid, ethylene glycol methacrylate phosphate (EGMP) and 2-acrylamido-2-methyl-1-propane sulfonic acid) with a crosslinker (methylenebisacrylamide) in the pores of poly(propylene) host membranes. The functionalized membranes thus obtained were characterized by gravimetry, FTIR spectroscopy, radiotracers and scanning electron microscopy for the degree of grafting and water uptake, presence of functional groups, ion-exchange capacity, and physical structure of the membranes, respectively. The uptakes of Cs(+), Ag(+), Sr(2+), Cd(2+), Hg(2+), Zn(2+), Eu(3+), Am(3+), Hf(4+) and Pu(4+) ions in the functionalized membranes were studied as a function of acidity of the equilibrating aqueous solution. Among the functionalized membranes prepared in the present work, the EGMP-grafted membrane (with phosphate groups) showed acid concentration dependent selectivity towards multivalent metal ions like Eu(3+), Am(3+), Hf(4+) and Pu(4+). The solvent extraction studies of EGMP monomer in methyl isobutyl ketone (MIBK) solvent indicated that divalent and trivalent metal ions form complexes with EGMP in 1:2 proportion, but the distribution coefficients of trivalent metal ions were significantly higher that for the divalent ions. The uptakes of Eu(3+) ions in monomeric EGMP (dissolved in MIBK) and polymeric EGMP (in the forms of crosslinked gel and membrane) were studied as a function of concentration of H(+) ions in the equilibrating solution. This study indicated that polymeric EGMP has better binding ability towards Eu(3+) as compared to monomeric EGMP. The variation of distribution coefficients of Eu(3+)/Am(3+) in gel and membrane as a function of H(+) ion concentration in the equilibrating aqueous solution indicated that ionic species held in the membrane and gel were not same. These results indicated that proximity of functional groups (phosphate) plays an important role in metal ion binding with polymeric EGMP.

Multicomponent diffusion studies were carried out in a poly(perfluorosulfonated) ion-exchange membrane, Nafion-117, using two cations, namely Na+ and Cs+, having widely different self-diffusivity and selectivity. Radiotracers were used to follow the time dependent concentration of the competing ions in the membrane. The studies were carried out at three different composition of the equilibrating solution. At all composition of the equilibrating solutions, the Na+ ion concentration was found to pass through a maximum, while the Cs+ ion concentration continuously increased till equilibrium is reached. This could be explained as being due to higher diffusivity but lower selectivity of Na+ ions than Cs+ ions. An attempt was made to reproduce the time profile of the competitive diffusion for both the ions using the modified form of Maxwell–Stefan formalism. The observed trend could be qualitatively explained using this approach.

Angular distributions of fission fragments have been measured in 24 Mg + 192 Os and 24 Mg + 197 Au reactions at E lab = 128 MeV which is close to entrance channel Coulomb barrier. Experimental angular anisotropies were in reasonably good agreement with those calculated using the statistical theory. Analysis of the angular distribution data of the present study and of our earlier measurement in 19 F + 197 Au reaction has shown that contribution from non-compound nucleus fission in these systems is not significant.

The selectivity of an anion-exchange polymer inclusion membrane (PIM) towards a number of anions (F − /OH − /HCO 3 − /CH 3 COO − /IO 3 − /Cl − /BrO 3 − /NO 2 − /Br − /NO 3 − /SCN − /MnO 4 − /ClO 4 − ) was studied with respect to I − ions using 131 I radiotracer. The PIM was prepared by physical immobilization of a liquid anion-exchanger trioctylmethylammonium chloride (Aliquat-336) into polymer matrix of cellulose triacetate (CTA) plasticized with 2-nitrophenyl octyl ether (NPOE). The highly hydrated ions (F − /OH − /HCO 3 − /CH 3 COO − /IO 3 − /Cl − ) did not exchange appreciably with I − counterion present in the membrane sample, while the less hydrated ions like ClO 4 − were strongly exchanged. The averaged selectivity coefficients ( K I − X − ) for those anions, which were appreciably exchanged with I − ions (Br − , NO 2 − , BrO 3 − , NO 3 − , SCN − , and ClO 4 − ) in the membrane, were determined from ion exchange isotherms. Attempt was made to theoretically evaluate the observed selectivity trends based on the Marcus formalism, which is commonly used for the calculation of selectivity coefficient in solvent extraction involving liquid ion exchangers. The model reproduced well the experimentally observed selectivity coefficients using the adjusted dielectric constant of the membrane medium. The dielectric constant of the plasticizer (NPOE) was not found to be appropriate for prediction of experimentally measured selectivity coefficients.

The self-diffusion coefficients of water and ions were used to study the physical (tortuosity) and electrostatic interactions of counterions in poly(perfluorosulfonic) acid membrane (Nafion-117) matrix. The self-diffusion coefficients of water ( D H 2 O m ) were measured in the water swollen Nafion-117 membrane with Zn2+, Ca2+, Sr2+, and Fe2+ counterions by analyzing the experimental exchange rates between tritium tagged water (HTO) in membrane and equilibrating water. In order to study the effects of equilibrating solution, the HTO-desorption rate profiles between the membrane samples in H+ or Cs+ forms and equilibrating solution containing CsCl or HCl (0.25 mol/L) were measured. It was observed that the HTO-exchange rate profile was slower in case of membrane sample in Cs+-from equilibrated with salt/acid solution than that equilibrated with deionized water in same ionic form. However, HTO-exchange rate profile did not alter in case of H+-form of membrane on equilibration with salt or acid solution. The variation of ln D H 2 O m with polymer volume function Vp/(1 − Vp), where Vp is polymer volume fraction, indicated that: (i) D H 2 O m in the membrane with multivalent counterions was lower than that reported for membrane with monovalent counterions at same Vp, and (ii) the linear trends observed in variation of ln D H 2 O m with Vp/(1 − Vp) for multivalent and monovalent counterions were significantly different. The values of D H 2 O m in membrane normalized with D H 2 O m at Vp = 0 were taken as an estimate of the tortuosity factor for self-diffusion of ions in the membrane matrix. The self-diffusion coefficients of ions reported in the literature along with tortuosity factor obtained from D H 2 O m in the corresponding ionic forms of the membrane were analyzed to obtain the charge (Zi) independent electrostatic interaction parameter g(φ) of monovalent and divalent ions in the membrane. This analysis indicated that g(φ) also vary exponentially as a function of Vp/(1 − Vp) irrespective of charge on counterions. In order to study the influence of Vp on diffusional transport rates of Na+ and Cs+ ions in membrane, a permeation experiment was carried out using H+-form of membrane having high water volume fraction. The diffusional transport rates of Cs+ and Na+ in H+-form of membrane were found to be similar indicating that the water volume fraction in membrane has strong influence on the parameters that govern the diffusion across the Nafion-117 membrane.

Nine combinations of scintillating optode samples were prepared using three different matrix-forming polymers (cellulose triacetate (CTA)/polyvinyl toluene (PVT)/poly methyl methacrylate (PMMA)) plasticized with three different plasticizers (dioctyl phthalate (DOP)/tri-(2-ethylhexyl)phosphate (TEHP)/tri-(2-ethylhexyl)trimelitate (TOT)). One of these has been reported earlier for quantitative preconcentration and determination of α-emitting actinides. The absorption–emission spectra were used to optimise the type of plasticizer, amounts of primary scintillator (2,5-diphenyl oxazole (PPO)) and secondary scintillator (1,4-bis(2-methylstyryl)benzene (MSB)) in these optodes. The results suggest that TEHP is the best-suited plasticizer for all the matrix-forming polymers. Among them, the scintillator molecules immobilized in the TEHP plasticized PVT matrix produced higher α-scintillation pulse height than that in other matrices. However, the extraction efficiency of 241 Am was found to be significantly lower (∼80%) in PVT/PMMA-based optodes as compared to CTA-based optodes (∼98%). Since the optode integrates preconcentration and signal generation steps, the PVT and PMMA polymers could not be used as matrix-forming polymer in the scintillating optode due to poor extraction efficiency of bis(2-ethylhexy)phosphoric acid (HDEHP) in these matrices. The TEHP plasticized CTA optode containing optimum amounts of scintillators and HDEHP was found to have optimum extraction efficiency for trivalent actinides, reusability and better α-scintillation efficiency than similar system developed earlier.

The formation of silver nanoparticles by chemical reduction of Ag+-loaded Nafion-117 membrane with NaBH4 was studied using radioactivity tagged ions. The counterion-exchange method (Ag(m)+--Na(s)+) was used to obtain a membrane sample with a varying proportion of Ag+ ions. The X-ray elemental mapping across the thickness of the membrane by energy-dispersive X-ray spectrometer attached to the environmental scanning electron microscope (ESEM/EDAX) indicated that Na+ and Ag+ were uniformly distributed in the membrane samples before reduction. The average size of nanoparticles formed after reduction was found to be 15 +/- 3 nm, irrespective of the concentration of silver ions present in the membrane before reduction. Energy-dispersive X-ray fluorescence (EDXRF) analyses of the membrane samples, carried out before and after reduction, indicated that the Ag concentration on the membrane surface was considerably increased after reduction. EDXRF measurements of the membrane samples, obtained from reduction carried out in a dead end cell, indicated that Ag nanoparticles were formed only on the membrane surface exposed to NaBH4 solution. Reduction carried out with NaBH4 tagged with 22Na showed that the formation of Ag nanoparticles involved exchange of Ag+ ions from ion-exchange sites in the interior of the membrane with Na+ ions, followed by reduction of Ag+ ions with BH4- ions at the surface of membrane. The study of self-diffusion of water, Na+, and Cs+ ions in the membrane loaded with Ag nanoparticles indicated that formation of Ag nanoparticles did not affect the diffusional transport properties of the membrane. The ion-exchange capacity and water uptake capacity were also not affected by the formation of Ag nanoparticles in the membrane. The spatial distribution of Ag nanoparticles across the thickness of the membrane obtained by ESEM/EDAX showed that Ag nanoparticles were confined to a few-micrometer surface layer of the membrane. Based on these observations, an attempt has been made to explain the mechanism of the formation of Ag nanoparticles in the membrane.

Excitation functions of reaction products formed in16O +66Zn and37Cl +45Sc systems, leading to the same compound nucleus,82Sr, were measured using recoil-catcher technique and off-line γ-ray spectrometry. The contribution of non-compound processes like transfer and incomplete fusion (ICF) reactions to the cross-sections of different evaporation residues were delineated by comparing the experimental data with the predictions of Monte Carlo simulation code PACE2. The results show that non-compound processes become a significant fraction of the total reaction cross-section in16O +66 systems in the beam energy range studied, while37Cl +45Sc gives mainly compound nucleus products. The mass asymmetry dependence of the fusion and non-compound cross-sections have been analysed in terms of the static fusion model and sum rule model

Summary Plasticized anion-exchange polymer inclusion membranes (PIM) were prepared by physical immobilization of a liquid anion-exchanger trioctylmethylammonium chloride (Aliquat-336) into the polymer matrix of cellulose triacetate (CTA) plasticized with 2-nitrophenyl octyl ether (NPOE). The self-diffusion coefficients (D m) of I− ion in these PIMs were obtained by analysing the experimental 131I radiotracer exchange rates with an analytical solution of Fick's second law. The D m was found to increase exponentially as a function of volume fraction of liquid (plasticizer) in the membrane, which can be attributed to reduction of physical obstruction in diffusion path of the ions in CTA polymer matrix. The selectivity of PIMs towards different anions, with respect to I− ion, was obtained from a determination of mole fraction of I− ion (ratio of moles of I− ion to total ion-exchange sites) in the membrane as a function of mole fraction of I− ion in the equilibrating aqueous solution containing a competing X− ion (X− = F−/Cl−/Br−/NO3 −/ClO4 −). This study indicated that the PIM has preference for I− ion in the presence of Cl−, Br− and NO3 − ions in equilibrating solution, while ClO4 − ion are preferred over I− ion. The selectivity trend (ClO4 −>I−>NO3 −>Br−>Cl−>F−) in PIM was found to correspond with Hofmeister series.

We measured the excitation functions for nine evaporation residues for the 12C + 115In system in the energy range well beyond the Coulomb barrier. The experimental results are compared with the theoretical values calculated using the Monte Carlo simulation code PACE2. Several complete and incomplete fusion products are observed in the present study. It is observed that a definite amount of incomplete fusion contribution is present, even at the lowest energy. The results clearly show the incomplete fusion contributions in the iodine and antimony products.

Backscattering spectrometry employing 4 MeV proton beam has been used to nondestructively measure the oxygen concentration in holmium, thulium and thorium metal foils. Such foils are used as targets for nuclear physics experiments. Significant amount of oxygen was found in these metallic targets due to their oxidation by atmospheric oxygen. Tungsten oxide was used as a standard to determine the scattering cross-section of 4 MeV protons by oxygen.

The scintillating polymer inclusion membrane (S-PIM) was developed for preconcentration and determination of α-emitting actinides from aqueous solution. The preparation of S-PIM involved physical immobilization of an extractant bis(2-ethylhexyl)phosphoric acid, primary scintillator 2,5-diphenyloxazole, and secondary scintillator 1,4-bis(2-methylstyryl)benzene in the plasticized cellulose triacetate matrix. The S-PIM was found to be effective for the quantitative sorption (94–98%) of trivalent lanthanides/actinides ( 147 Pm , 154 Eu and 241 Am ), tetravalent actinides (Pu(IV)) and hexavalent actinides (U(VI)) from the aqueous solutions whose acidity had been adjusted to pH 2.5, 1.0 and 0.25 mol/L, respectively with dilute HNO3. The interference of β-emitting lanthanides, in preconcentration and determination of α-emitting actinides using S-PIM, were also studied. The α-scintillation counting efficiency in the S-PIM was found to be 92–95% after discriminating the background noise. However, β-scintillation counting efficiency was found to be in the range of 12–25% depending upon the energy of β-particles. It was observed that β-scintillation pulses from 147 Pm and 154 Eu could be discriminated based on pulse height analysis. Thus, α-activities of the actinides sorbed in the sample of S-PIM could be directly measured in the presence of β-emitters by scintillation counting. However, the α-scintillation counting efficiency was reduced to 38% after discriminating β-scintillation pulses in the S-PIM. The preconcentration ability of S-PIM was examined in tap water and seawater spiked with 241 Am . The total α-activity of 46 Bq (present in 100 mL) could be preconcentrated and measured from tap water using S-PIM.

Recoil range distribution of evaporation residues formed in complete and incomplete fusion of 82.5 MeV 12 C and 13 C with 181 Ta have been measured by recoil catcher technique followed by off-line gamma-ray spectrometry. The recoil range distributions of incomplete fusion products were found to be in good agreement with that simulated on the basis of direct surface transfer reaction model. The cross-sections for complete and incomplete fusion were delineated from the measured excitation function data at the same beam energy. The fraction of incomplete fusion in the total cross-section was found to be more in the case of 12 C than that in the case of 13 C indicating the dependence of incomplete fusion probability on the cluster structure of the projectile.

Polymer inclusion membranes based on cellulose triacetate polymer, containing 2-nitrophenyloctyl ether as plasticizer and dinonyl napthalene sulfonic acid as cation exchanger were loaded with Cs+ and Ag+ and were studied by backscattering spectrometry technique to measure the distribution of the metal ions across the membrane using a proton beam. The study showed that the distribution of the metal ions across the membrane is uniform, thereby suggesting the uniform distribution of the cation exchanger. This indicates that the hydrophilic nature of the sulfonic acid group in the cation exchanger does not significantly influence its distribution in the predominantly hydrophobic matrix of cellulose triacetate. However, the microstructure of the membrane, obtained by atomic force microscopy, shows the formation of blobs on the surface of the PIM indicating the inhomogeneity at the sub-micron scale.

Summary Absolute γ ray intensities in the decay of 194Tlg have been measured following the radiochemical separation of 194Pb produced in the reaction of 19F+181Ta. The (EC+β +) branching ratios in the decay of 194Tlg to various levels of 194Hg were deduced. Three new levels are introduced in the decay scheme. A precise value of half life of 194Pb (10.0±0.4 min) is reported.

Kinetic-energy spectra and angular distribution of projectile-like fragments have been measured in the reaction of 84 MeV 12C on 169Tm, using the surface barrier silicon-based ΔE-E telescopes. The fragments close to the projectile show typical spectra of quasi-elastic transfer reactions, which were found to be in agreement with the calculations based on the direct surface transfer reaction model. A significant cross-section of fast alpha-particles was found at forward angles, reminiscent of incomplete fusion reactions, which could be explained in terms of the direct surface transfer reaction model after taking into account the level density of continuum states in the heavy reaction product. The results have been explained in terms of the continuous evolution of the reaction mechanism as a function of the mass transfer.

SummaryFormation cross sections of about forty fission products have been determined using recoil catcher technique followed by off line gamma-ray spectrometry in7Li induced fission of232Th atElab= 41.9, 36.6 and 31.4 MeV. The measured data have been used to deduce charge and mass distributions. Mass distribution is found to be asymmetric at all the three energies. Cross sections of evaporation residues formed in both transfer reactions (232,233,234Pa) as well as in complete fusion (234Np), have also been measured. The measured evaporation residue cross sections and the decay probabilities of target like nuclei (233,234,235Pa) formed in the various transfer reactions, as calculated by PACE2, have been used to estimate the transfer induced fission cross sections. The data indicated that the magnitude of transfer induced fission is very small.

Background: Detailed studies on the effect of the breakup of weakly bound projectile on fission are scarce. Distinguishing the events of compound nuclear (CN) fission from the breakup or transfer induced fission to understand the properties of measured fission fragments is difficult but desirable.Purpose: To investigate the effect of projectile breakup and its breakup threshold energy on fission-fragment (FF) mass distributions and folding angle distributions for $^{6,7}\mathrm{Li} + ^{238}\mathrm{U}$ reactions and find out the differences in the properties of the fission events produced by complete fusion (CF) from the total fusion (TF).Methods: The FF mass and folding angle distributions have been measured at energies around the Coulomb barrier using gas detectors by time-of-flight technique. The results are compared with the ones involving tightly bound projectiles as well as predictions from systematics to bring out the effect of the breakup.Results: A sharp increase in the peak to valley (P:V) ratio of FF mass distribution with the decrease in bombarding energy for $^{6,7}\mathrm{Li} + ^{238}\mathrm{U}$ reactions is observed when all events are assumed to be CN fission. As the beam energy falls through the fusion barrier, the full width half maximum (FWHM) of the FF folding angle distribution is found to increase at sub-barrier energies, unlike the reactions involving tightly bound projectiles where a linear decrease in FWHM is expected. By selecting pure CN events from the scatter plot of the velocity components of the composite nuclei, the energy dependence of the deduced FWHM is found to be consistent with the ones involving tightly bound projectiles. Similarly, the P:V ratio obtained for the selected CN events is consistent with the theoretical calculations as well as the experimental data for the proton induced reaction forming similar CN.Conclusions: The presence of projectile breakup induced fission and a relatively low breakup threshold for $^{6}\mathrm{Li}$ compared to $^{7}\mathrm{Li}$ explains the observed differences in the energy dependence of the P:V ratio and the FWHM of FF folding angle distributions for CF and TF fission in the present reactions.

The angular distribution of projectile-like fragments (PLFs) in the 19F + 159Tb reaction have been measured at beam energy equal to 98MeV. Angular distributions of PLFs showed a systematic change with increasing mass transfer, starting from the peaking at grazing angle for heavier PLFs to very forward peaked angular distributions for lighter PLFs. Cross-sections of the different PLFs were obtained by integrating their centre-of-mass angular distributions. The PLF cross-sections have been compared with the incomplete fusion cross-sections obtained from the earlier measurement of the evaporation residue cross-section. Reduced cross-sections for lighter PLFs were observed to be higher compared to those observed in 19F + 66Zn reaction at similar values of E cm/V b. Also, elastic scattering measurements were carried out to get information about the grazing angle and total reaction cross-section.

Elastic, inelastic and inclusive alpha cross sections have been measured. Coupled-channels calculations by including the couplings of projectile breakup channels and target excitations explain the measured elastic and inelastic data. The inclusive alpha particle production is found to be more than two-third of the total reaction cross section. From coupled-channels calculations, the contribution of α from the non-capture α -d breakup of the 6 Li projectile is calculated to be very small. It suggests the possibility of many transfer induced breakup channels, having α as one of the breakup fragments, to be responsible for such a large α particle production.

Cross-sections for projectile-like fragments (PLFs) have been measured in the 24Mg$ + $59Co reaction at E lab = 93 , 100 and 108MeV to investigate the projectile structure effect in incomplete fusion (ICF) reactions. In this study, the cross-sections for ICF channels involving the emission of Ne, O and C were found to be higher than the other ICF channels involving the emission of odd Z PLFs. This observation was attributed to the alpha cluster structure of the 24Mg nucleus. Significant cross-sections for incomplete fusion reactions at these beam energies indicated that the collision trajectories with l < l crit are contributing to ICF.

Angular distributions of projectile-like fragments (PLFs) have been measured in the reaction $^{19}\mathrm{F}+^{66}\mathrm{Zn}$ at ${E}_{\mathrm{lab}}=61,82,92$, and 109 MeV to understand their formation in the low energy domain ($ \ensuremath{\lesssim}7$ MeV nucleon). In this energy range, maximum angular momentum `${l}_{\mathrm{max}}$' in the reaction is lower than or close to the critical or limiting angular momentum for complete fusion `${l}_{\mathrm{lim}}$(CF).' The sum-rule model was modified to explain the cross sections of PLFs in the present study. For the first time, the modified sum-rule model, with a competition of incomplete fusion (ICF) reaction with complete fusion below ${l}_{\mathrm{lim}}$(CF) reasonably reproduced the cross sections of PLFs in the beam energy range of the present study. It was observed that the cross sections of lighter PLFs fall more rapidly with decreasing beam energy compared to those of heavier PLFs, suggesting a change in the reaction mechanism from heavier to lighter PLFs. Transfer probabilities for peripheral collisions were calculated within the framework of a semiclassical formalism. The parameters of the nuclear potential required for the calculation of transfer probability were obtained by fitting the elastic scattering data measured in the present work. Calculated transfer probabilities were significantly lower compared to the corresponding experimental values, suggesting a significant overlap of the projectile and the target nuclei in incomplete fusion reactions. The present analysis showed that the overlap of the projectile and the target nuclei increases with increasing mass transfer at a given beam energy and for a given PLF, overlap increases with increasing beam energy.

Palm shell obtained from coastal part of southern India was studied for the removal for the adsorption of Hg (II) ions. Batch adsorption experiments were carried out as a function of pH, concentration of Hg (II) ions, time, temperature and adsorbent dose. Maximum removal was seen in the range pH 4.0- pH 7.0. The palm shell powder used as adsorbent was characterized for its surface area, SEM, PXRD, FTIR, ion exchange capacity, moisture content, and bulk density, soluble content in water and acid and pH. The experimental results were analyzed using Langmuir I, II, III, IV and Freundlich adsorption isotherms. The batch sorption kinetics was studied for the first order reversible reaction, pseudo first order; pseudo second order reaction and the intra-particle diffusion reaction. The biomass was successfully used for removal Hg (II) from synthetic and industrial effluents and the technique appears industrially applicable and viable., {"references":["Chojnacki, A., Chojnacka K., Hoffmann J., Gorecki H., 2004. The\napplication of natural zeolites for Hg removal from laboratory tests to\nindustrial scale. Minerals Engineering. 17, 933-937.","Akshu, Z., 2002. Determination of the equilibrium, kinetic &\nthermodynamic parameters of the batch biosorption of Ni (II) ions onto\nchleorella vulgaris. Process Biochem. 38, 89-99.","Gupta, V., Srivastava, A., Jain N., 2001. Biosorption of Chromium (VI)\nfrom aqueous solutions by green algae Spirrogyra species. Wat. Res. 35\n(17), 4079-4085.","Bailey, S., Olin, T., Bricka, R., Adrian D., 1999. A review of potentially\nlow-cost sorbents of heavy metals. Water Res. 33 (11), 2469-2479.","Donmez, G., Akshu, Z., Ozturk, A, Kutsal, T., 1999. A comparative\nstudy on heavy metal biosorption characteristic of some algae. Process\nBiochem. 34, 885-892.","Figueria, M., Volesky, B., Ciminelli, V., Roddick, F., 2000. Biosorption\nof metals in brown seaweed biomass. Water Res. 34 (1), 196-204.","Loukidou, M., Matis, K., Zouboulis, A., Kyriakidou, M., 2003. Removal\nof As (V) from waste waters by chemically modified fungal biomass.\nWater Res. 37, 4544-4552.","Davis, T., Volesky, B., Mucci, A., 2003. A review of the biochemistry of\nheavy metal biosorption by brown algae. Water Res. 37 (18), 4311-4330.","Ma, W., Tobin, J., M., 2003. Development of multimetal binding model\n& application to binary metal biosorption onto peat biomass. Water Res.\n37, 3967-3977.\n[10] Nabizadeh, R., Naddafi, K., Saeedi, R., Mahvi, A.H., Vaezi, F.,\nYaghmaeian, K., Nazmara, S., 2005. Kinetic and equilibrium studies of\nLead & Cd biosorption from aqueous solutions by Sargassum SPP.\nBiomass. Iran. J. Environ. Health. Sci. Eng. 2 (3), 159-168.\n[11] Vinod, V., Anirudhan, T., 2002. Sorption of tannic acid by zirconium\npillared clay. J Chem Technol Biotechnol. 77, 92-101.\n[12] Quek, S., Wase, D., Forster, C.F., 1998. The use of sago waste for the\nsorption of lead and copper. Water S. A 24, 251-256.\n[13] Abia, A., Horsfall, M., Jnr., O., Didi, 2003. The use of chemically\nmodified and unmodified cassava waste for the removal of Cd, Cu and\nZn ions from aqueous solution. J. Bioresource Technol 37, 4913-4923.\n[14] Low, K., Lee, C., Leo, A., 1995. Removal of metals from electroplating\nwastes using banana pith. Bioresour. Technol. 51, 227-231.\n[15] Randall, J., Hautala, E., Waiss, A., 1974. Removal and recycling of\nheavy metal ions from agricultural byproducts. Proc. 4th Mineral waste\nutilization symp. Chicago, IL USA.\n[16] Gardea-Torresdey, J., Gonzalez, J., Tiemann, K., Rodrignuez, O.,\nGamez, G., Alfalfa, G., 1998. Phytofiltration of Hazardous cadmium,\nchromium, lead and zinc ions by biomass of Medicago sativa (Alfalfa).\nJ. Hazard. Mater. 48, 191-206.\n[17] Shan, Ho.Y., Wase, D., Forster, C., 1996. Removal of lead ions from\naqueous solution using sphagnum moss peat as adsorbent. Water SA 22,\n219-224.\n[18] Ckowksi, P., Joshi, V., 2007. Adsorption kinetics study for the removal\nof Ni (II) & Al (III) from an aqueous solution by natural adsorbents.\nDesalination 208, 216-231.\n[19] Shan, Ho.Y., Kay, G.Mc., 1998. Kinetic models for the sorption of dye\nfrom aqueous solution by wood. Process Safety and Environmental\nProtection. 76B, 183-191.\n[20] Namasivayam, C., Kardivelu, K., 1999. Uptake of mercury (II) from\nwastewater by activated carbon from an unwanted agricultural solid byproduct:\ncoirpith Carbon 37, 79-84.\n[21] Shan, Ho.Y., 2004. Citation review of Lagergren kinetic rate equation on\nadsorption reactions. Scietometrics 59 (1), 171-177.\n[22] Michelsen, L., Gideon, P., Pace, E., Kutal, L., 1975. Removal of soluble\nHg from water by complexing techniques. U. S. D. I., Office of Water\nResearch & Tech. Bull 74.\n[23] Vogel-s Textbook of Practical Organic Chem. including Qualitative\nInorganic Analysis, 4th Ed., Longman Scientific & Technical 1978, 450-\n470.\n[24] Guibal, E., 1998. Metal-Anion Sorption by Chitosan Beads: Equilibrium\nand Kinetic Studies. Ind. Eng. Chem. Res. 37, 1454-1463.\n[25] Shan, Ho.Y., Kay, G.Mc., 2000. The kinetics of sorption of divalent\nmetal ions onto sphagnum. Water Res. 34 (3), 735-742.\n[26] Shan, Ho.Y., 2006. Second order kinetic model for the sorption of Cd\nonto tree fern: A comparision of linear and non-linear methods. Water.\nRes. 40, 119-125.\n[27] Abdelwaheb, O., 2007. Kinetic and isotherm studies for Cu (II) removal\nfrom waste water using various adsorbents. Egyptian Journal of Aquatic\nResearch, 33 (1), 125-143.\n[28] Weber, W., Morris, J., 1963. Kinetics of adsorption on carbon from\nsolution. Sanit. Eng. Div. Am. Soc. Civ. Engg. 89 (SA2), 31-40.\n[29] Patil, S., Bhole, A., Natrajan, G., 2006. Scavenging of Ni(II) Metal Ions\nby Adsorption on PAC and Babhul Bark. Journal of Environ. Science &\nEngg. 48 (3), 203-208.\n[30] Dudhich, A., Khasim, Bibi, S., Kavita, G., 2004. Adsorption of Ni (II)\nusing Agrowaste, Rice Husk, Journal of Environmental Science and\nEngg. 46 (3), 179-185.\n[31] Low, K., Lee, C., Lee K.P., 1993. Sorption of copper by dye-treated oilpalm\nfibers. Bioresour. Technol. 44, 109-112.\n[32] Murugesan, G., Sathishkumar, M., Swaminathan, K., 2006. Arsenic\nremoval from groundwater by pretreated waste tea fungal biomass.\nBioresource. Technol. 97, 483-487."]}

Fission fragment angular distributions were measured in {sup 11}B+{sup 243}Am reaction in the beam energy (E{sub lab}) range of 60-72 MeV. Experimental anisotropies in {sup 11}B+{sup 243}Am reaction were found to be higher than the values calculated using the statistical theory indicating contribution from noncompound nucleus fission. For {sup 11}B+{sup 243}Am reaction, entrance channel mass asymmetry is higher than the Businaro-Gallone critical mass asymmetry. Observation of anomalous fission fragment angular distribution in {sup 11}B+{sup 243}Am reaction possibly indicates that the target deformation plays an important role in deciding the contribution from noncompound nucleus fission.

Angular distribution of fission fragments have been measured for $^{19}\mathrm{F}+^{197}\mathrm{Au}$ reaction at bombarding energies from 91 to 110 MeV. Fission fragment angular distributions have been calculated by transition state model with the transmission coefficients obtained using the coupled-channels theory. The calculated angular anisotropies are in good agreement with the experimental anisotropies. The experimental fission cross sections have also been reproduced on the basis of the coupled-channels theory. The results of angular distribution measurement do not show any significant contribution from quasifission as was reported in the literature based on the measurement of evaporation residues and mass distribution.

Berkelium isotopes have been produced in 11B-induced reaction on 238U. The EC decay of 244Bk → 244Cm has been studied by carrying out the single and coincidence measurements of the γ-rays emitted during the de-excitation of the 244Cm levels. Radiochemical separations have been carried out to minimize the contribution from the fission products and target. The new half-life of 244Bk is obtained as 5.02 ± 0.03 h, which is close to the theoretically calculated value. The relative intensities of the decay γ-rays have been re-evaluated. Based on the coincidence measurements, a tentative partial level scheme for 244Bk → 244Cm decay has been proposed.