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A study on the crystal structure of monoclinic HfO2 has been performed using synchrotron X-ray and neutron diffraction data separately, as well as a combination of both. The precision of the structural parameters increases significantly due to application of the neutron diffraction technique. The experimental oxygen positions in HfO2, derived precisely, are visualized only by semi-local density functional calculations in terms of the calculated electronic band gap, but are not captured as accurately by using hybrid functionals.

A systematic study of orthorhombic phase formation at ambient conditions beyond a critical concentration of dopant Tantalum (Ta) in HfO 2 is reported. The effect on the path of structural evolution...

In this study, various detector configurations have been investigated in order to explore the optimal condition for decay rate measurements of radioactive samples using gamma spectroscopy technique. A limitation of detecting low energy gamma rays from decaying radioactive nuclei, is the Compton background which can be significantly reduced by rejecting Compton scattered events through active Bismuth germanate (BGO) shielding. On the other hand, for a CLOVER detector without BGO shielding, one can place the radioactive samples very close to the detector for enhancing geometrical efficiency. A single crystal High Purity Germanium (HPGe) detector can also be used for decay rate measurements. In order to measure the decay rate of nuclei decaying via gamma emission with reasonable intensity, optimal close geometry options have been investigated for various HPGe detector configurations.

The study of liquid–gas phase transition in heavy-ion collisions has generated a lot of interest among the nuclear physicists in recent years. In heavy-ion collisions, there is no direct way of measuring the state variables like entropy, pressure, energy, and hence, unambiguous characterization of phase transition becomes difficult. This work proposes new signatures of phase transition that can be extracted from the observables which are easily accessible in experiments. It is observed that the temperature dependence of the first-order derivative of the order parameters in nuclear liquid–gas phase transition exhibit similar behavior as that of the variation of specific heat at constant volume \(C_v\) which is an established signature of first-order phase transition. This motivates us to propose these derivatives as confirmatory signals of liquid–gas phase transition. The measurement of these signals is easily feasible in most experiments as compared to the other signatures like specific heat, caloric curve, or bimodality. Total multiplicity, size of the largest cluster are some of the order parameters which have been studied. Statistical models based on canonical ensemble and lattice gas model has been used for the study. This temperature where the peak appears is designated to be the transition temperature and the effect of certain parameters on this has also been examined. The multiplicity derivative signature proposed in this work has been further confirmed by other theoretical models as well as in the experimental study.

A study on the crystal structure of monoclinic HfO

Low lying states of 150Sm have been studied through decay spectroscopy of odd–odd 150Pm, populated with 150Nd(p, n)150Pm reaction at E b e a m = 8.0 MeV using 97% enriched 150Nd target and detecting the γ-rays with the VENUS array comprised of six Compton suppressed Clover HPGe detectors. Nineteen new transitions are placed, four tentative γ-rays are confirmed and eight transitions are found to have altered placements; consequently assigning thirteen new levels to the decay scheme of 150Pm. The spin-parity assignments of the excited levels of 150Sm were made based on logft and angular correlation analysis.

Time Differential Perturbed Angular correlation (TDPAC) study of pressure dependent phase transition in HfO2 has been performed for the first time to reveal the change in local structure around Hf atom. The results show that the nuclear hyperfine interaction parameters namely, quadrupole interaction frequency and asymmetry parameter at atmospheric pressure are in agreement with literature while that at 45 GPa are significantly different from that at atmospheric pressure.

Result from electronic structure calculations with precisely measured atomic structure of HfO2 is reported in this work. Several experimental works have been done with structure of HfO2 but its O-positions are not precisely measured yet, to the best of our kowledge. Thus, present computational works based on the first-principle calculations are performed with relaxed bulk structuresthat do not match the experimental parameters. Recently we have found precise structural parameters experimentally. Therefore first time electronic structure calculations were performed with precisely measured atomic structure of HfO2. Full-potential calculation was done with Perdew, Burke and Ernzerhof (PBE)-GGA formulation of exchange correlation potential for the preliminary ground state computation of band gap. Then hybrid modified Becke-Johnson (mBJ) potential was applied on top of PBE-GGA computed wave function to estimate the band gap.

We have studied the change of decay rate of 7Be implanted in the small Pd lattice versus large Pb lattice. Since the electron affinities of Pd and Pb are very low and similar, any observed increase of the decay rate of 7Be could be attributed to the compressional effect in the smaller confinement of Pd lattice. It has been found that the decay rate of 7Be is faster in Pd lattice compared to that in Pb lattice by (0.82± 0.16)%. Similar results were observed by applying high external pressure on 7BeO lattice. Density functional calculations underpredict the increase of 7Be decay rate under compression by a large factor. It is important to understand this result because of its significance in calculating 7Be decay rate in the solar core and corresponding 8B neutrino flux.

Pressure induced structural change of HfO 2 was extensively studied up to 10 GPa with diffraction technique using synchrotron X-ray radiation. The experiment drew attention as ambiguities still exist over the monoclinic to orthorhombic evolution of HfO 2 at high pressure condition. Rietveld refinement of the diffraction patterns leads to determination of the detailed structure of HfO 2 at different pressures. The space group of its first orthorhombic phase is confirmed. Density functional calculations were carried out to understand the pressure induced phase transition. High temperature study of this material was also performed up to 1373 K (1100 0 C) using synchrotron X-ray source for studying suitability of the material in high temperature applications and precise thermal expansion coefficients are reported.

A high quality factor helical resonator is required for the non-destructive resonant detection of eigen-frequencies of charged particles confined in a Penning trap. A 20 MHz helical resonator has been designed utilizing both the analytical and numerical methods. The performance of the helical resonator has been studied extensively by varying its dimensions and properties of the materials. The design parameters have been optimized and a prototype resonator is fabricated. The important parameters of the resonator like resonance frequency, quality factor, effective inductance and capacitance have been measured. The results obtained from the finite element analysis method are in good agreement with the experimentally measured values. It has been found that the distance between the radiofrequency probe and the open end of the helix plays an important role in maximizing the power coupling between the input and output terminals. Simulation studies have been performed to study the variation of power coupling with the change in the length of the probe and its radial position inside the resonator. The results have been verified experimentally. The maximum power coupling has been obtained by varying the length of the probe, where the resonance frequency and Q-factor were kept nearly same as the unloaded condition. The tank circuit with increased power coupling can be utilized to detect the feeble trap signal with high quality factor.

We have developed and tested a compact non-magnetic feedthrough made of epoxy resin and capable of maintaining vacuum leak tightness over a wide temperature range (300 K-4 K). It is equipped with 15 electrical pins and three 50 Ω coaxial lines. The feedthrough has been designed to apply a high voltage (up to 5 kV) and transmit radio-frequency signals for operating a Penning trap over a wide temperature range (300 K-4 K). The characteristic impedances of the coaxial lines have been measured at 300 K and 77 K and found to remain ∼50 Ω over the frequency range of our interest (10 MHz-80 MHz). The details of its fabrication and performance over a wide temperature range have been discussed.

After publication of the paper, the authors realized that one of the references was not correct. Its correct version appears in this erratum.

The cyclotron at Variable Energy Cyclotron Centre (VECC), Kolkata, has recentlyrecently completed its 40 years of operation in 2017. During the past four decades, VECC has been able to cross several milestones in exploring the properties of nuclei with the help of low energy light as well as heavy ions accelerated by the cyclotron. In this review, we endeavour to present an overall picture of the intense research activities in various branches of nuclear physics carried out in the past four decades using cyclotron, with special emphasis on the important achievements in each field.

Hafnium oxide (HfO2) is a technologically important material. This material has K-value of 25 and band gap 5.8 eV. A k value of 25–30 is preferred for a gate dielectric [1]. As it shows good insulating and capacitive properties, HfO2 is being considered as a replacement to SiO2 in microelectronic devices as gate dielectrics. On the other hand because of toughening mechanism due to phase transformation induced by stress field observed in these oxides, HFO2 has been a material of investigations in various configurations for a very long time. However the controversies about phase transition of HfO2 under pressure still exists. High quality synchrotron radiation has been used to study the structural phase transition of HfO2 under pressure.

Measurement of M, the total multiplicity, for central collision between comparable mass heavy ions can provide a signature for first order phase transition. The derivative of M with respect to E*/A where E* is the excitation energy in the centre of mass and A the total mass of the dissociating system is expected to go through maximum as a function of E*. Theoretical modelling shows that this is the energy where the specific heat Cv maximizes which typically happens at first order phase transition. The measurement of total M is probably feasible in more than one laboratory., 4 pages, 7 figures

This paper presents the design and implementation of an in situ measurement setup for the capacitance of a five electrode Penning ion trap (PIT) facility at room temperature. For implementing a high Q resonant circuit for the detection of trapped electrons/ions in a PIT, the value of the capacitance of the trap assembly is of prime importance. A tunable Colpitts oscillator followed by a unity gain buffer and a low pass filter is designed and successfully implemented for a two-fold purpose: in situ measurement of the trap capacitance when the electric and magnetic fields are turned off and also providing RF power at the desired frequency to the PIT for exciting the trapped ions and subsequent detection. The setup is tested for the in situ measurement of trap capacitance at room temperature and the results are found to comply with those obtained from measurements using a high Q parallel resonant circuit setup driven by a standard RF signal generator. The Colpitts oscillator is also tested successfully for supplying RF power to the high Q resonant circuit, which is required for the detection of trapped electrons/ions.

To increase the signal to noise ratio, helical resonator is generally employed in between trap signal pick up electrode and Low noise amplifier having high input impedance. Based on available literature and simulation study, a 20MHz Helical resonator was designed and fabricated. The measured resonant frequencyand quality factor of the fabricated resonator is 19.67 MHz and 1030 respectively. Simulation results are found in good agreement with the fabricated resonator parameter. Effect of material’s conductivity on the quality factor of the resonator is also studied.

The end point energies of nuclear $\beta$ decays have been measured with a segmented planar Ge LEPS detector using both singles and coincidence techniques. The $\beta - \gamma$ coincidence has been performed with a segmented planar Ge LEPS and a single 10$\%$ HPGe detector. The $\gamma$ ray and $\beta$ particle responses of the Segmented planer Ge LEPS detector were studied using monte carlo simulation code GEANT3. The experimentally obtained $\beta$ spectrum was in reasonably good agreement with the simulation results. The experimental end point energies are determined with substantial accuracy for some of the known $\beta$ decays in $^{106}$Rh, $^{210}$Bi and $^{90}$Y. The end point energies corresponding to three weak branches in $^{106}$Rh $\rightarrow$ $^{106}$Pd decay has been measured for the first time., Comment: 12 pages, 8 figures and 1 table

We present an analysis of a doubly compensated, open ended, cylindrical Penning ion trap including the effect of realistic gaps between adjacent electrodes. This work is a generalization of the work of X. Fei, W.M. Snow, Nuclear Instruments and Methods A 425(1999) 431. By varying the lengths of the electrodes, we have been able to make the trap dynamically orthogonalized and tune out higher order anharmonicities up to C8 term over a wide range of inner radii of the cylindrical trap and gap lengths between adjacent electrodes. This work should help to generate a higher quality quadrupolar potential near the center of the cylindrical trap and be useful for studies involving high precision measurements of the trapped particles.

We have prepared the Hafnium Oxide (HfO2) nano-particles using precipitation method. We performed the ambient pressure X-ray diffraction (XRD) using Cu-Kα. We determined the particle size from full width half maxima (FWHM) and applying Scherrer’s method. We also did the high pressure x-ray diffraction (XRD) studies at Elettra Synchrotron Source, Trieste. We observe shift in peak positions and FWHM with pressure in our high pressure XRD data which indicate stress and particle size effect in the sample with compression.

The study of liquid gas phase transition in fragmentation of nuclei in heavy ion collisions has been extended to the strangeness sector using the statistical model for multifragmentation. Helmholtz's free energy, specific heat and few other thermodynamic observables have been analyzed in order to examine the occurence of phase transition in the strange matter. The bimodal behaviour of the largest cluster formed in fragmentation also strongly indicates coexistence of both the phases. The presence of hyperons strengthens the signals and also shifts the transition temperature to lower values., 5 Pages, 7 Figures

The thermal behavior of hafnium dioxide fiber has been investigated with the aid of time differential perturbed angular correlation (TDPAC) technique along with XRD and SEM measurements. This study has proved a good thermal stability of the fibrous material up to 1173 K and the fiber loses its crystallinity to a meager extent at 1673 K. No phase transition has been observed up to 1673 K in this fiber. TDPAC parameters for the HfO 2 fiber annealed at 1173 K are ω Q =124.6 (3) Mrad/s and η =0.36 (1). These values remain unaltered for the HfO 2 fiber annealed even at 1673 K. Electronic structure calculations based on the density functional theory (DFT) for HfO 2 doped with tantalum impurity have been performed and the calculated EFG parameters are in reasonable agreement with the experimental values.

Penning Ion trap is an instrument where charged particles can be stored by means of quadrupolar electric field and high magnetic field. Motion of charged particle within the trap electrodes induces weak image signal which is detected by LC resonant circuit followed by a Low noise amplifier. To get a large voltage signal, the quality factor of the resonator should be very high. So, a high Q helical resonator is commonly used in ion trapping devices, as it offers considerably high Q (~ 1000) in a small geometry. Resonating frequency of the resonator is selected based on the trap geometry and mass of trapped particle. For ion trapping system we have designed a 20 MHz helical resonator and studied its parameters through simulations.

Role of Zr atom on the quadrupole interaction of 181Ta in rutile TiO2 has been investigated by time differential perturbed angular correlation (TDPAC) study. The quadrupole frequency remains same as that in the pure rutile TiO2 but its distribution increases with the amount of Zr. This indicates a metal-metal interaction between probe atom and Zr-atom in the nearest neighbour.

The eigenstate energies of an atom increase under spatial confinement and this effect should increase the electron density of the orbital electrons at the nucleus thus increasing the decay rate of an electron capturing radioactive nucleus. We have observed that the orbital electron capture rates of 109In and 110Sn increased by ( 1.00 ± 0.17 ) % and ( 0.48 ± 0.25 ) % respectively when implanted in the smaller Au lattice compared to implantation in a larger Pb lattice. These observations are interpreted to be a result of the higher compression experienced by the large radioactive atoms in the smaller spatial confinement of the Au lattice.

In this paper we describe the design, implementation and performance of a low noise cascode amplifier. This amplifier is characterized in term of equivalent input voltage noise density and voltage gain at different drain currents upto a frequency of 80 MHz. The equivalent input voltage noise density of this amplifier is measured by two techniques. In the first technique, the output noise spectrum is downconverted to an intermediate frequency and the noise voltage is acquired using a data acquisition card interfaced with LabView software. Whereas, in the second technique, a spectrum analyzer is used to measure the equivalent input voltage noise density. The equivalent input voltage noise desnity measured by both techniques is found to be less than (1.8 ± 0.2) nV/√Hz in the band (30–80) MHz.

This paper presents the design and test results of a low noise amplifier indigenously developed for VECC cryogenic Penning ion trap facility. The amplifier is built in two stages of which the first stage provides signal amplification whereas the second stage offers an output impedance of 50 Ω. The voltage gain as well as input voltage noise density of the amplifier is measured at room temperature and 130K. In this paper, we have demonstrated that cooling the amplifier down to 130K increases the voltage gain by a factor ∼ 1.5 and decreases the input voltage noise density by a factor ∼ 1.7.

We comment on a recently published paper that has demonstrated that the increase in the electron-capture nuclear decay rate of $^{7}\mathrm{Be}$ in $^{7}\mathrm{BeO}$ under compression can be accounted for by the phase transformation of BeO from the wurtzite to the rock-salt structure.

We shall discuss about the scientific motivation and construction of a 7×7 BaF2 crystal array at Variable Energy Cyclotron Centre, Calcutta. This detector would be used to measure high energy γ-ray photons from GDR decay and proton-neutron bremsstrahlung reactions at the present 88″ cyclotron and upcoming superconducting cyclotron at VECC, Calcutta. This detector can also be used to measure photons from quark-gluon plasma at the relativistic heavy ion collider (RHIC) in USA.

We find from our measurements that the decay rate of 7 Be implanted in Au is lower than that implanted in Al 2 O 3 by a relatively large amount (0.72±0.07)%. This result and others have been analyzed quantitatively using the linear muffin-tin orbital (LMTO) method and Hartree's calculations. Our results are important for accurately extracting the nuclear matrix element of the astrophysically significant 7 Be + e − → 7 Li + ν reaction.

30 keV 111mCd and 50 keV 199mHg beams from ISOLDE were used to implant on preformed targets of C60 with a thickness of 1 mg cm-2. Endofullerene compounds, viz. 111mCd@C60 and 199mHg@C60 formed during implantation were separated by filtration through micropore filter paper followed by solvent extraction. Dried samples of the endofullerene compounds were counted for the time differential perturbed angular correlation (TDPAC) measurement using the coincidence of the 151 - 245 keV cascade of 111mCd and the 374 - 158 keV cascade of 199mHg on a six LaBr3(Ce) detector system coupled with digital electronics. The results for 111mCd@C60 indicate a single static component (27%) and a fast relaxing component (73%), the latter implying that the cadmium atom moves rapidly inside the cage at room temperature. The quadrupole interaction frequency and asymmetry parameter of the cadmium atom occupying the static site in C60 are wQ=8.21(36) Mrad s-1 and η = 0.41(9), respectively. The fast relaxation constant is 0.0031(4) ns-1. Similarly, mercury atoms also exhibit a single static and a fast component. The static site has a quadrupole frequency wQ=283.0(12.4) Mrad s-1 and η =0 with a fraction of 30%. The fast relaxation constant is 0.045(8) ns-1 with a fraction of 70%, very similar to that of cadmium.

Electron capture (EC) decay of ${}^{146}$Gd (${t}_{\frac{1}{2}}=48$ d) to the low lying states of ${}^{146}$Eu has been studied using high-resolution $\ensuremath{\gamma}$-ray spectroscopy. The ${}^{146}$Gd activity was produced by ($\ensuremath{\alpha},2n$) reaction at ${E}_{\ensuremath{\alpha}}=32$ MeV using a 93.8$%$ enriched ${}^{144}$Sm target. The level structure has been considerably modified from the measurement of $\ensuremath{\gamma}$-ray singles, $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidences and decay half lives. Lifetime measurement has been performed for the 3${}^{\ensuremath{-}}$ (114.06 keV) and 2${}^{\ensuremath{-}}$ (229.4 keV) levels of ${}^{146}$Eu using the mirror symmetric centroid difference (MSCD) method with LaBr${}_{3}$ (Ce) detectors. The lifetimes for these two states have been found to be 5.38 $\ifmmode\pm\else\textpm\fi{}$ 2.36 ps and 8.38 $\ifmmode\pm\else\textpm\fi{}$ 2.19 ps respectively. Shell model calculation has been performed using oxbash code in order to interpret the results.

This paper presents an improved model for the prediction of bandwidth enhancement factor (BWEF) in an inductively tuned common source amplifier. In this model, we have included the effect of drain-source channel resistance of field effect transistor along with load inductance and output capacitance on BWEF of the amplifier. A frequency domain analysis of the model is performed and a closed-form expression is derived for BWEF of the amplifier. A prototype common source amplifier is designed and tested. The BWEF of amplifier is obtained from the measured frequency response as a function of drain current and load inductance. In the present work, we have clearly demonstrated that inclusion of drain-source channel resistance in the proposed model helps to estimate the BWEF, which is accurate to less than 5% as compared to the measured results.

We discuss recent results of E.B. Norman et al. [Phys. Lett. B 519 (2001) 15] in relation to our earlier work [A. Ray et al., Phys. Lett. B 455 (1999) 69] and point out that the apparent disagreement between the two sets of experimental results is most likely due to the choice of different reference samples with which the comparisons have been done. In addition, the irradiation by heavy ion beam might also damage the lattice structure of the medium and such effect was not included in our calculations. We think that our earlier conclusion regarding the downward revision of predicted 8B solar neutrino flux by ≈2% should stand.

In this paper we describe the design and development of cryogenic electronic instrumentation required for VECC cryogenic Penning ion trap facility. As a part of the development of cryogenic electronic instrumentation, a low noise amplifier based on GaAs technology is designed and room temperature testing of the amplifier is successfully accomplished. The equivalent input voltage noise density of the amplifier measured at room temperature is found to be in the range of (1.8.2)nV Hz at the ion trap axial frequency of 63 MHz. Also a cryogenic switching and RC filtering circuit is developed in order to maintain proper switching of RF energy used to excite the motional amplitude of trapped electrons. These RC filtering circuits filter the noise in the DC supply lines. The performance of this circuit board has been tested successfully upto 90K.

The half-life of exohedral {sup 7}Be-C{sub 60} complex and that of {sup 7}Be implanted in a gold foil have been found to be about the same within {approx_equal}0.2%. Using a radiochemical technique, we also measured that the probability of formation of endohedral {sup 7}Be-C{sub 60} complex by nuclear implantation technique was (5.6 {+-} 0.45)%. We also find that the half-life of endohedral {sup 7}Be-C{sub 60} complex is shorter than that of exohedral complex by more than 1%. An analysis of these results using linear muffin-tin orbital method calculations indicates that most of the implanted {sup 7}Be ions in fullerene C{sub 60} stay at a distance of {approx_equal}5.3 A from the centers of nearest C{sub 60} molecules forming exohedral compounds and those who enter the fullerene cages go to the centers of the cages forming endohedral {sup 7}Be-C{sub 60} compounds.

The inclusive α-particle spectra from 16 O+ 89 Y, 12 C+ 93 Nb, and 16 O+ 93 Nb reactions around 6-7 MeV/nucleon incident energy (laboratory) have been studied. These spectra have been fitted very well using an algebraic expression for the statistical emission of particles from the compound nucleus and subsequent daughter nuclei. We do not find any statistically significant oscillations in the remaining spectra after subtracting out the contributions due to initial and sequential emissions from the compound nuclei, thus showing no direct evidence for the existence of α particles as independent particles in the nuclei.

The inclusive energy distributions of fragments $(3l~Zl~7)$ emitted in the reaction ${}^{16}\mathrm{O}{+}^{27}\mathrm{Al}$ at ${E}_{\mathrm{lab}}=116\mathrm{MeV}$ have been measured in the angular range ${\ensuremath{\theta}}_{\mathrm{lab}}=15\ifmmode^\circ\else\textdegree\fi{}\char21{}115\ifmmode^\circ\else\textdegree\fi{}.$ A nonlinear optimization procedure using multiple Gaussian distribution functions has been proposed to extract the fusion-fission and deep-inelastic components of the fragment emission from the experimental data. The angular distributions of the fragments, thus obtained, from the deep-inelastic component are found to fall off faster than those from the fusion-fission component, indicating shorter lifetimes of the emitting dinuclear systems. The lifetimes of the intermediate dinuclear configurations have been estimated using a diffractive Regge-pole model. The lifetimes thus extracted $[\ensuremath{\sim}(1\char21{}5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\mathrm{sec}]$ are found to decrease with the increase in the fragment charge. Optimum Q values are also found to increase with increasing charge transfer, i.e., with the decrease in fragment charge.

We discuss in the framework of linear muffin-tin orbital method and Bahcall’s calculations how the ratio of Lto K-shell electron capture rates (L/K ratio! in Be would be affected by the host medium in which Be is implanted. Our calculations show that the recently observed discrepancy between the measured and observed L/K ratio in Be could be understood quantitatively as a result of in-medium effects distorting the L-shell electron orbital of Be.

A new technique has been developed wherein one of the relatively short lived isotopes of europium (, Half life days) has been generated by decay of parent atoms and the ions are confined in a Paul trap for spectroscopic studies. Studies of the mass dependent ion oscillation frequencies show that the ions trapped have a mass number 146 amu and this was confirmed by similar measurements carried out on trapped barium and potassium ions. From calculations of thermal ionization probabilities based on the Langmuir–Saha equation and the number of trapped ions estimated from ion response signal, the approximate number of the different isobars (of mass number 146) trapped, has been evaluated. We also present simulations of the evolution of laser-induced fluorescence photons of the trapped ions, wherein a pulsed laser is used to excite the resonance - transition, which rapidly decays to the metastable states emitting fluorescence photons.

The low-lying states of odd-odd 132 I, the 3p-3h nucleus with respect to the doubly magic 132 Sn, have been characterized from decay spectroscopy. The neutron rich Iodine and Tellurium isotopes have been produced as fission product of alpha-induced fission of 235 U and radiochemically separated. The life-time of the first excited state of 132 I have been precisely measured using LaBr3(Ce) scintillators from the decay of 132 Te. The IT decay of the high spin isomer (8 - ) in 132 I has been measured with a Low Energy Photon Spectrometer (LEPS) of segmented planar Ge detector.

We find that in contrast to the large orbiting yield seen in $^{28}\mathrm{Si}$${+}^{12}$C, $^{24}\mathrm{Mg}$${+}^{16}$O, $^{24}\mathrm{Mg}$${+}^{12}$C, and $^{20}\mathrm{Ne}$${+}^{12}$C reactions, the back-angle, strongly damped binary yields from $^{4}\mathrm{He}$${+}^{27}$Al and $^{4}\mathrm{He}$${+}^{40}$Ca reactions are in agreement with the predictions of statistical compound nuclear reaction. These results disagree with the observation from heavy-ion reaction systematics that the orbiting yield will dominate whenever the number of open channels is small, and suggest that the weak absorption and surface transparency of nucleus-nucleus interaction are not sufficient conditions for the dominance of orbiting in back-angle, strongly damped reaction.

The News of the Week article “Tweaking the clock of radioactive decay” (29 Oct., p. [882][1]) by Richard A. Kerr focuses on the finding by Chih-An Huh ([1][2]), published in Earth and Planetary Science Letters , that beryllium-7 decays at a different rate depending on what form it is in (hydrated ion, hydroxide, or oxide). However, relatively large variations in the decay rate of beryllium-7 in different environments had already been reported before Huh published his results. About 4 months before Huh's publication, we published an article ([2][3]) reporting that the decay rate of beryllium-7 implanted in gold is slower than when it is implanted in Al2O3 by a relatively large amount (0.72%). This result and many others have been understood using the linear muffin-tin orbital (LMTO) method and Hartree's calculations, and the implications of these results in different fields have been discussed ([2][3]). Before our work, W. K. Hensley et al. ([3][4]) applied a high pressure of up to 270 kilobars to 7BeO and found that the decay rate increased by 0.59%. In his article, Chih-An Huh reports that the decay rate of beryllium-7 is about 1.0% faster when the beryllium is in the chemical form Be2+(OH2)4, as compared with BeO. Earlier, however, H. W. Johlige et al. ([4][5]) also measured the difference between the decay rates of beryllium-7 in the same matrices and found it to be (0.0374 _ 0.0077)% faster as compared with BeO. They also measured the differences of beryllium-7 decay rates in many other chemical forms and detected only tiny variations of the order of 0.1% ([4][5]). Such differing results have yet to be discussed. 1. [↵][6] Chih-An Huh, Earth Planet. Sci. Lett. 171, 325 (1999). 2. [↵][7]1. A. Ray 2. et al. , Phys. Lett. B 455, 69 (1999). [OpenUrl][8] 3. [↵][9]1. W. K. Hensley, 2. W. A. Basset, 3. J. R. Huizenga , Science 181, 1164 (1973). [OpenUrl][10][Abstract/FREE Full Text][11] 4. [↵][12]1. H. W. Johlige, 2. D. C. Aumann, 3. H. J. Born , Phys. Rev. C2, 1616 (1970). [OpenUrl][13] [1]: /lookup/doi/10.1126/science.286.5441.882 [2]: #ref-1 [3]: #ref-2 [4]: #ref-3 [5]: #ref-4 [6]: #xref-ref-1-1 "View reference 1 in text" [7]: #xref-ref-2-1 "View reference 2 in text" [8]: {openurl}?query=rft.jtitle%253DPhys.%2BLett.%2BB%26rft.volume%253D455%26rft.spage%253D69%26rft.atitle%253DPHYS%2BLETT%2BB%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [9]: #xref-ref-3-1 "View reference 3 in text" [10]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.issn%253D0036-8075%26rft.aulast%253DHensley%26rft.auinit1%253DW.%2BK.%26rft.volume%253D181%26rft.issue%253D4105%26rft.spage%253D1164%26rft.epage%253D1165%26rft.atitle%253DPressure%2BDependence%2Bof%2Bthe%2BRadioactive%2BDecay%2BConstant%2Bof%2BBeryllium-7%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.181.4105.1164%26rft_id%253Dinfo%253Apmid%252F17744291%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [11]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEzOiIxODEvNDEwNS8xMTY0IjtzOjQ6ImF0b20iO3M6MjU6Ii9zY2kvMjg3LzU0NTYvMTIwMy45LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [12]: #xref-ref-4-1 "View reference 4 in text" [13]: {openurl}?query=rft.jtitle%253DPhys.%2BRev.%26rft.volume%253DC2%26rft.spage%253D1616%26rft.atitle%253DPHYS%2BREV%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx