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Management of plastic, rubber and cellulosic waste from various industries is a challenging task. An engineering scale plasma pyrolysis based incinerator has been commissioned for incineration of combustible waste, including plastic, rubber and cellulose. Operational trials of wastes with simulated composition show a weight reduction factor of more than 18 and volume reduction factor of more than 30. The volume reduction factor is tenfold higher than the compaction process currently practised for rubber and plastic wastes. Representative residual ash samples derived from these runs are subjected to their elemental analysis using EDXRF technique and results are comparable with the published literature. Relative variation of individual elements is attributed to the type of waste and feed composition. Analysis is aided with the calculation of index of geoaccumulation, enrichment factor (EF), contamination factor (CF) and pollution load index (PLI). From this study, it is evident that S, Cr, Zn, As, Se, Hg and Pb are of concern for environment in residual ash from plasma incineration of combustible waste. The efficacy of the incineration process is evaluated; C, H and O reduction achieved is more than 98% and overall enrichment ratio (ER) for the inorganic elements is more than 4.5. This study highlights the importance of elemental composition for the performance analysis of the plasma based incineration as well as hazards evaluation of constituents in residual ash for its further management.

Spectroscopic gas sensors rely on spectral data of molecules available from various databases for analysis of gases. The total internal partition sums (TIPS) for molecules is one of the essential parameter needed for analysis of gases using their absorption spectrum. The calculated values of TIPS are reported by many researchers and are available in tabulated form in HITRAN database. The database is useful in many industrial gas sensors. These sensors require fast response along with portability. However, storing and recalling the TIPS data adds to the computational cost and time. For such applications, a polynomial expression for recalling the TIPS values is a fast and convenient method. The present study provides the polynomial coefficients for TIPS as a function of temperature for the rapid recall of data listed in the HITRAN 2016. The entire temperature range 70–3000 K is covered in three sets of temperatures for polynomial fitting. The lowest-order polynomial expressions which can model the variation of TIPS with temperature with better than 1% accuracy are listed for 49 molecules (125 isotopologues) for the ease of recall. The coefficients of polynomials up to fifth order are also provided in supplementary material for applications requiring higher accuracy. The data will be useful in the research and development of spectroscopic gas sensing technology.

Temperature dependent studies of optical transmission profiles of CaF2 crystals in the range 12–300 K are performed using vacuum ultraviolet (VUV) synchrotron radiation. The observed spectral profiles near the transmission edgeare fitted using the universal Urbach tail expression modified appropriately to incorporate the effects of residual gases present in high vacuum (10-6 mbar) systems. Satisfactory fit of the experimental data is obtained by including fitting parameters representing scattering and absorption by deposited layers, predominantly due to water. Details of the experimental setup, results and analysis of the data are discussed.

The electronically excited states of ethyl bromide and its deuterated isotopologue (C2H5Br and C2D5Br) are studied using synchrotron radiation based photoabsorption spectroscopy in the wavenumber region 50 000–86 000 cm−1. A detailed spectral analysis supported by quantum chemical calculations is presented. A complex Rydberg series structure comprising of nsa1, npa1, npe, nda1 and nde series, converging to each of the two spin–orbit split components of the first ionization potential (2E3/2 and 2E1/2) is observed for both the isotopologues. Quantum defect values are consistent with excitation from Br lone pair orbitals. Rydberg series analysis is extended to several higher members as compared to earlier work and corroborates the dominance of the spin–orbit mechanism over the hyperconjugative effect. A few new Rydberg series members converging to the second and third ionization potentials are observed and assigned. The complete gas phase VUV photoabsorption spectrum of C2D5Br up to its first ionization limit and its infrared absorption spectrum in the liquid phase are reported for the first time. An extended vibronic analysis of bands accompanying the first few Rydberg series is reported along with several new assignments. DFT calculations on ground states of neutral and ionic species and TDDFT calculations on singlet and triplet excited states aid and support the spectral analysis. Potential energy curves with respect to the C–Br bond length and the C–C–Br bond angle provide further insights into the nature of the excited states. This work represents a comprehensive study of the electronic absorption spectrum of ethyl bromide and its deuterated counterpart.

In(Ga)As/GaAs-based quantum dot infrared photodetectors (QDIPs) are among the most efficient devices in the mid-wavelength infrared and long-wavelength infrared regions for various defense and space application purposes. Considering the importance of the results reported so far on In(Ga)As/GaAs QDIPs, here we had tried to develop a post-growth method for enhancing QDIP characteristics using both low energy and high energy light ion (hydrogen) implantations. The field-assisted tunneling process of dark current generation was suppressed due to the hydrogen ion implantation, even at a very high operational bias. A stronger multicolor photo-response was obtained for devices implanted with low energy hydrogen ions. From experimental results, we proposed a device model which explains the improved QDIPs performance caused by hydrogen ion implantation. (C) 2016 Elsevier Ltd. All rights reserved.

The gas phase electronic absorption spectrum of nitrobenzene (C6H5NO2) in the 4.5–11.2 eV region is recorded using synchrotron radiation with a view to comprehend the nature of the excited states. Electronic excited states of nitrobenzene are mainly classified as local excitations within the benzene ring or nitro group and charge transfer excitations between the benzene and nitro group, with some transitions showing percentage from both. The nature of molecular orbitals, their orderings and energies are obtained from density functional theory calculations which help in assigning partially assigned/unassigned features in earlier photoelectron spectroscopy studies. Optimized geometry of ionic nitrobenzene predicts redistribution of charge density in the benzene ring rather than the nitro group resulting in stabilization of the benzene ring π orbitals in comparison to the neutral molecule. Time dependent density functional theory computations are found to describe the experimental spectra well with respect to energies, relative intensities and nature of the observed transitions in terms of valence, Rydberg or charge transfer type. New insights into the interpretation of 1B2u←1A1g and 1B1u←1A1g shifted benzene transitions in light of the present computational calculations are presented. The first few members of the ns, np and nd type Rydberg series in nitrobenzene, converging to the first six ionization potentials, identified in the spectra as weak but sharp peaks are reported for the first time. In general, transitions to the lowest three unoccupied molecular orbitals 4b1, 3a2 and 5b1 are valence or charge transfer in nature, while excitations to higher orbitals are predominantly Rydberg in nature. This work presents a consolidated experimental study and theoretical interpretation of the electronic absorption spectrum of nitrobenzene.

Computational studies of electronically excited states of the acetone molecule [(CH3)2CO] and its fully deuterated isotopologue [(CD3)2CO] are performed using the time dependent density functional (TDDFT) methodology. In addition to vertical excitation energies for singlet and triplet states, equilibrium geometries and vibrational frequencies of the n=3 Rydberg states (3s, 3p and 3d) are obtained. This is the first report of geometry optimization and frequency calculations for the 3px, 3pz, 3dyz, 3dxy, 3dxz, 3dx2–y2 and 3dz2 Rydberg states. Results of the geometry optimization indicate that the molecule retains approximate C2V geometry in most of these excited Rydberg states, with the most significant structural change seen in the CCO bond angle which is found to be reduced from the ground state value. Detailed comparison of the computationally predicted vibrational wavenumbers with experimental studies helps to confirm several of the earlier vibronic assignments while leading to revised/new assignments for some of the bands. The important role of hot bands in analysis of the room temperature photoabsorption spectra of acetone is corroborated by this study. While the vibrational frequencies in excited Rydberg states are overall found to be close to those of the ionic ground state, geometry optimization and vibrational frequency computation for each excited state proves to be very useful to arrive at a consistent set of vibronic assignments. Isotopic substitution helps in consolidating and confirming assignments. An offshoot of this study is the interpretation of the band at ~8.47 eV as the π–3s Rydberg transition converging to the second ionization potential.

Background: Scrub typhus is becoming an increasing cause of meningitis/meningoencephalitis in endemic areas. Materials and Methods: We conducted a retrospective chart review to describe epidemiological features, clinical characteristics, laboratory profile, and therapeutic outcomes in scrub typhus, considering meningitis/meningoencephalitis as cases and patients without meningoencephalitis as controls. Results: A total of 97 scrub typhus positive cases confirmed by immunoglobulin M enzyme-linked immunosorbent assay and/or polymerase chain reaction were included in the study. By univariant analysis, risk factors such as exposure to a forest, adolescent age and associated oliguria were significantly higher among cases as compared to the control group. Signs and symptoms that were significantly higher among meningitis/meningoencephalitis cases were conjuctival suffusion, pharyngitis, maculopapular rash, pain in the abdomen, splenomegaly, and altered sensorium. Cerebrospinal fluid (CSF) pictures closely resembled aseptic meningitis. All patients had received doxycycline or azithromycin, and the outcome was favorable in the case group. Conclusion: Scrub typhus meningitis/meningoencephalitis was significantly higher in adolescents. Close observation and great care is essential for adolescent patients with associated risk factors. Prompt treatment ensures survival.

An experimental set-up for studying photophysics and photochemistry of molecules in an inert gas medium (matrix-isolated) and in the ice phase at low temperatures has been developed and commissioned at the Photophysics beamline, Indus-1 synchrotron radiation source. This end-station uses an in-house-developed closed-cycle cryostat for achieving cryo-temperatures (∼10 K). Synchrotron radiation from the Photophysics beamline is used as the source of UV–VUV photons and the system is equipped with a Fourier transform infrared spectrometer for characterization of the molecular species formed at low temperature. Various individual components of the end-station like closed-cycle cryostat, experimental chamber, gas mixing and deposition systems are tested to ascertain that the desired performance criteria are satisfied. The performance of the composite system after integration with the Photophysics beamline is evaluated by recording IR and UV–VUV photoabsorption spectra of sulfur dioxide at low temperatures (10 K), both in the ice phase as well as isolated in argon matrices. Results obtained are in good agreement with earlier literature, thus validating the satisfactory performance of the system. As an off-shoot of the study, the VUV absorption spectrum of matrix-isolated SO2 in argon matrix up to 10.2 eV is reported here for the first time. This experimental end-station will provide new opportunities to study photon-induced reactions in molecules of environmental, astrochemical and industrial importance. Details of the design, development and initial experimental results obtained are presented.

The vacuum ultraviolet (VUV) photoabsorption spectra of the dihalomethanes \(\rm CH_2X_2 \ (X=Cl, Br, I)\) are studied using synchrotron radiation in the energy region 6–11.8 eV (\(\sim\)49,000–95,200 cm\(^{−1}\)). A detailed comparison is made to identify similarities, differences and trends in the spectra and excited state structure of these three molecules. The electronic spectra of the dihalomethanes in this region are dominated by Rydberg series of \(ns\), \(np\) and \(nd\) type. Quantum defect analysis reveals that the Rydberg series in all the dihalomethanes originate from the four outermost halogen lone pair non-bonding orbitals. On going from Cl to I, the energy difference between the first four ionization potentials decreases which as a consequence leads to spectral congestion and complications in spectral assignments. In all three molecules, several Rydberg transitions are accompanied by vibrational structure. A notable common feature seen in the vibronic structure is the excitation of the \(\nu_3\) (\(\rm C\)\(\rm -\)\(\rm X\) symmetric stretch) mode to form extensive progressions. Additionally, the \(\nu_1\) (\(\rm C\)\(\rm -\)\(\rm H\) symmetric stretch), \(\nu_2\) (\(\rm CH_2\) bend) and \(\nu_8\) (\(\rm CH_2\) wag) modes are observed in \(\rm CH_2Cl_2\) and \(\rm CH_2I_2\), although they do not form long progressions. Quantum chemical calculations of ground and excited states are used to support the analysis and an improved theory-experiment comparison is provided for \(\rm CH_2Br_2\).

This study reports enhancements in photoluminescence (PL) efficiency resulting from implanting InAs/GaAs quantum dots with high energy protons without any post-annealing treatment and discusses the effects that result from varying the capping layer over dots. The PL efficiency for proton-implanted samples increased when the fluence of the 3 MeV protons improved from 8.0 x 10(11) to 1.0 x 10(13) ions/cm(2). Up to a certain point, variations in the proton energy level improved the PL efficiency. The improvements in PL efficiency resulted from annihilation of defects and non-radiative recombination centers from the dots and capping layer. Increments in the thermal activation energy of the implanted samples confirmed the finding. To determine the validity of the improvement on the optical properties of the dots, we implanted an InGaAs/GaAs quantum dot infrared photodetector (QDIP) heterostructure with 3 MeV protons. The implanted QDIP exhibited suppressed dark current density and enhanced peak detectivity by two orders compared to the as-grown devices. (C) 2015 Elsevier B.V. All rights reserved.

Photoabsorption and photodissociation studies of dimethyl sulphoxide and its deuterated isotopologue (DMSO-h 6 and DMSO-d 6 ) are performed using synchrotron radiation in the 35,000–80,000 cm −1 region. In the photoabsorption spectrum, Rydberg series converging to the first three ionization potentials of DMSO at 9.1, 10.1 and 12.3 eV corresponding to removal of an electron from the highest three occupied molecular orbitals (14a′, 7a″ and 13a′) are observed. Based on a quantum defect analysis, Rydberg series assignments are extended to higher members as compared to earlier works and a few ambiguities in earlier assignments are clarified. Analysis is aided by quantum chemical calculations using the DFT and TDDFT methodologies. Vibronic structures observed in the spectrum of DMSO-h 6 in the regions 7.7–8.1 eV and 8.1–8.8 eV are attributed to the transitions 7a″→4p at 7.862 eV and 14a′→6s/4d at 8.182 eV, respectively. Photoabsorption spectra of DMSO-h 6 and -d 6 recorded using a broad band incident radiation show prominent peaks, which are identified and assigned to electronic and vibronic transitions of the SO radical. This provides a direct confirmation of the fact that DMSO preferentially dissociates into CH 3 and SO upon UV–VUV excitation, as proposed in earlier photodissociation studies. An extended vibronic band system associated with the e 1 Π–X 3 Σ − transition of the SO radical is identified and assigned. The complete VUV photoabsorption spectrum of DMSO-d 6 is also reported here for the first time.

The electronic absorption spectrum of N,N-dimethylformamide (DMF) is studied in the 45 000-80 000 cm-1 (5.6-9.9 eV) region using synchrotron radiation. The vacuum ultraviolet (VUV) spectrum comprises mostly of Rydberg series of ns, np, and nd types converging to the first two ionization potentials (IPs). Quantum defect values obtained are consistent with excitation of an electron from the highest occupied molecular orbitals localized on nitrogen (4a″) and oxygen (16a'); in addition, the 3s Rydberg transition converging to the third IP (3a″) is observed at 8.95 eV. A reinvestigation of the infrared spectrum of DMF in the 500-4000 cm-1 region with the help of density functional theory (DFT) calculations establishes the planarity of the ground state and leads to revision of several vibrational assignments. Vertical excited state energies and their valence/Rydberg character are predicted using time dependent DFT calculations; excellent correlation is achieved between theoretical results and experimentally observed spectral features. Potential energy curves of the first few excited states give additional insights into the nature of the excited states and their role in photodissociation dynamics. The absorption spectrum of DMF in the region >63 400 cm-1 (7.85 eV) as well as a complete set of spectral assignments in the VUV region (45 000-80 000 cm-1) is reported for the first time. This work represents a comprehensive study of the absorption spectra of DMF in the VUV and infrared regions.

A consolidated study of the VUV absorption spectra of CH2Cl2 and CD2Cl2 in the 50,000–95,000 cm−1 region using synchrotron radiation is presented. Rydberg series and vibronic analysis are carried out and supported by quantum chemical calculations. The broad absorption band of CH2Cl2 in the region 50,000–60,000 cm−1 is attributed to the valence states 11B2, 11B1 and 11A1. Most of the bands in the 60,000–95,000 cm−1 region are fitted to Rydberg series of ns, np and nd type converging to the first four ionization potentials 11.320, 11.357, 12.152 and 12.271 eV of CH2Cl2 arising from excitation of an electron from one of the four outermost Cl non-bonding orbitals (2b1, 3b2, 1a2 and 4a1). Vertical excited states of CH2Cl2 calculated using TDDFT are correlated with experimentally observed electronic states based on the symmetries of the initial and final MOs involved in a transition. A few Rydberg transitions viz. 2b1→5s, 4p, 5p, 6p; 3b2→4p, 5p; 1a2→4p are accompanied by vibronic features. Observed vibronic bands are assigned mainly to the CCl symmetric stretch (ν3′) mode with smaller contributions from the CH symmetric stretch (ν1′), CH2 bend (ν2′) and CH2 wag (ν8′) modes. Assignments are corroborated by comparison with the VUV absorption spectrum of the deuterated isotopologue CD2Cl2, reported here for the first time. The high underlying intensities seen in several sub-regions are explained by valence or valence–Rydberg mixed type transitions predicted with high oscillator strengths by the TDDFT calculations.

We report a comprehensive photoabsorption study of nitrous oxide (N2O) in the vacuum ultraviolet (45,000–95,000 cm−1) region using synchrotron radiation. The observed spectrum comprises of a few valence transitions and low lying Rydberg series converging to the two spin–orbit components (2П1/2,3/2) of the ground state of N2O+. Spectral analysis is aided by extensive quantum chemical calculations of vertical excited states, oscillator strengths and potential energy curves using the time dependent density functional theory. Vibronic bands observed in the first absorption system (45,000–60,000 cm−1) are assigned to hot band progressions in υ 2 ′ originating from v″=1 or 2. New insights into the assignment of the well-formed progression of bands in the X1Σ+→C1П system (60,000–72,000 cm−1) are afforded by consideration of the Renner–Teller interaction. A set of molecular vibrational parameters (ω2=467 cm−1, x22=−2.9, e=−0.24) for the C1П state are derived from a fitting of the experimental data. The 3pπ1Σ+ state at ~77,600 cm−1 shows a large quantum defect (0.96) which is explained as arising due to mixed valence–Rydberg character. In the 85,000–95,000 cm−1 region, a number of absorption features are observed with greater clarity than in earlier photoabsorption studies and assigned to Rydberg series of type nlλ (n=3,4; l=s,p,d; λ=σ,π,δ) and accompanying vibronic bands. This work has resulted in clarification of several discrepancies in earlier Rydberg series assignments. Additionally, the 3pπ 3Σ− Rydberg state at 85,788 cm−1, the valence transition 7σ→3π (1П) at 87,433 cm−1 and the 3dλ Rydberg series in the 91,700–92,600 cm−1 region are assigned for the first time.

The UV–VUV photoabsorption spectrum of dibromomethane (CH2Br2) in the energy region 4.3–11.8 eV (35,000–95,000 cm−1) is investigated using synchrotron radiation. Rydberg series converging to the first four ionization limits at 10.52, 10.74, 11.21 and 11.30 eV corresponding to excitations from the 3b1, 2b2, 1a2, and 4a1 orbitals of CH2Br2 are identified and analyzed. Quantum defect values are observed to be consistent with excitation from the bromine lone pair orbitals. Assignments of the ns Rydberg series are revised and the np and nd Rydberg series are assigned for the first time. Observed vibrational features accompanying the 5p and 4d Rydberg states are assigned exclusively to the totally symmetric (a1) –CBr symmetric stretching mode (ν3) in contrast to the earlier assignment to ν3 and –CH2 bending (ν2) modes. The Rydberg and valence transitions observed in the present experiment are found to be in good agreement with the vertical excited states calculated using the TDDFT method. The calculations are further used to infer the valence transitions responsible for the broad intensity pedestals underlying the Rydberg transitions. The assignments are confirmed using isotopic substitution studies on CD2Br2 whose UV–VUV photoabsorption spectrum is reported here for the first time. This work presents a consolidated analysis of the UV–VUV photoabsorption spectrum of dibromomethane.

We report here a comprehensive spectroscopic study of the absorption spectrum of the n-dodecane molecule using synchrotron radiation based photoabsorption and FTIR spectroscopy. Quantum chemical calculations using the DFT and TDDFT methodologies are used to predict relevant ground and excited state properties and correlate them with the experimental results. In the IR spectrum, assignment of the prominent CH stretching bands in the 2800–3000 cm−1 region are consolidated while a few new vibrational assignments are made in the 700–1500 cm−1 region. The electronic absorption spectrum of n-dodecane lies entirely in the vacuum ultraviolet (VUV) region and consists of a broad continuous absorption band starting from ∼7.5 eV, with no discernible structure. TDDFT calculations of vertical excited states predict that most of the excited states are Rydberg in nature. Potential energy curves of the first few excited states with respect to various bond lengths and bond angles are studied in order to gain additional insights into the nature of the excited states. The broad nature of the absorption is attributed partly to the effect of several conformers as well as hot bands from low frequency modes in the ground state and partly due to overlap of several Rydberg series converging to the first few ionization potentials (IPs). Energy separation between the first and second IP is theoretically predicted to be ∼0.65 eV, while successive separation between the second, third, fourth and fifth IPs is ∼0.03 eV. To the best of our knowledge this is the first report of the VUV absorption spectrum of n-dodecane in the region from 6 to 10 eV, as also the first report of theoretical calculations of its electronically excited states.

The VUV photoabsorption spectra of CHCl3 and CDCl3 in the energy region 6.2–11.8 eV (50,000–95,000 cm−1) have been investigated using synchrotron radiation from the Indus-1 source. Rydberg series converging to the first four ionization limits at 11.48, 11.91, 12.01 and 12.85 eV corresponding to excitation from the 1a2, 4a1, 4e, 3e, orbitals of CHCl3 respectively are identified and analyzed. Quantum defect values are observed to be consistent with excitation from the chlorine lone pair orbitals. Vibrational progressions observed in the region of 72,500–76,500 cm−1 have been reassigned to ν3 and combination modes of ν3+ν6 belonging to the 1a2→4p transition in contrast to earlier studies where they were assigned to a ν3 progression superimposed on the 3e→4p Rydberg transition. The assignments are further confirmed based on isotopic substitution studies on CDCl3 whose VUV photoabsorption spectrum is reported here for the first time. The frequencies of the ν3 and ν6 modes in the 4p Rydberg state of CHCl3 (CDCl3) are proposed to be ~454 (409) cm−1 and~130 (129) cm−1 respectively based on the vibronic analysis. DFT calculations of neutral and ionic ground state vibrational frequencies support the vibronic analysis. Experimental spectrum is found to be in good agreement with that predicted by TDDFT calculations. This work presents a consolidated analysis of the VUV photoabsorption spectrum of chloroform.

The VUV photoabsorption spectrum of acetone-d 6 is recorded in the energy region 6–10 eV using synchrotron radiation at a resolving power of∼1000. Extensive Rydberg series are observed converging to its first ionization limit (9.708 eV). Quantum defect analysis and vibronic analysis of higher Rydberg series members have been reported for the first time. A comparative study of the Rydberg series and accompanying vibronic structure observed in acetone-h 6 and acetone-d 6 has clarified and consolidated many of the vibronic assignments. The frequency of the ν 19 ′ mode (CO in-plane bend) of the 3p y state is obtained as 340±5 cm −1 on the basis of observation of an extensive progression of this mode.

The electronic absorption spectrum of acetone is revisited to evaluate the role of hot bands due to low lying torsional modes in the assignment of vibronic transitions. The UV–VUV photoabsorption spectrum of acetone is recorded in the energy region 3.5–11.8 eV at a resolution of � 4m eV at 4 eV and� 10 meV at 10 eV using synchrotron radiation. The absorption spectrum is dominated by richly structured Rydberg series (ns, np and nd) converging to the first ionization potential of acetone at 9.708 eV. Careful consideration of hot band contributions from torsional modes and symmetry selection rules have resulted in an improved set of vibronic assignments as compared to earlier room temperature work. Revised quantum defect values for some of the Rydberg transitions and a few new assignments in the nd series are also reported in this paper.

Gas phase photoabsorption studies of sulphur dioxide are carried out in the vacuum ultraviolet region using synchrotron radiation. Vibronic Analysis of the E ˜ − X ˜ system lying in the region 1400–1600 A is reported for the first time. A larger number of spectral features are resolved compared to earlier reports. While most of the observed bands can be arranged into four series with successive band spacing of 500–620 cm−1 in agreement with previous work, we observe two additional series with average separation of ∼1750 and ∼1000 cm−1. Results of the ab initio calculations suggest that at least three dominant excitations are involved in the E ˜ − X ˜ system viz. X ˜ A 1 1 → 3 A 1 1 , X ˜ A 1 1 → 2 A 2 1 and X ˜ A 1 1 → 2 B 1 1 . The observed vibrational features are found to be mainly due to excitation of the combination modes (ν1+ν2) and (ν2+ν3) with some contributions from ν1 and ν3. Details of the experiment and analysis are discussed in this paper.

A high resolution vacuum ultraviolet beamline has been developed and installed at the 450 MeV synchrotron source Indus-1 operating at the Raja Ramanna Centre for Advance Technology, Indore, India. This beamline is useful for photoabsorption studies of atoms and molecules in the VUV region of 1050–3000 A. The beamline consists of three major components: a pre-focusing optical system, a gas phase absorption setup and a 6.65 m vacuum ultraviolet spectrometer in off-plane Eagle mount. The performance of the beamline has been evaluated by recording VUV absorption spectra of xenon, oxygen and sulphur dioxide using synchrotron radiation from Indus-1. The resolution achieved is 0.1 A with a 1200 ln/mm grating. Spectra obtained agree well with the ones published earlier. Details of the design, development and performance testing of the beamline are discussed.

The vacuum ultraviolet (VUV) absorption spectrum of difluoromethane (CH2F2) was studied using synchrotron radiation from the storage ring Indus-1, Indore, India. Spectra were recorded in the spectral region 1050–1500 A (∼8.3–11.8 eV) at a resolution of 1.5 A. Three absorption band systems were observed in this region. Overall features observed are in good agreement with previously published work. Some discrepancies in assignments of the observed vibronic bands carried out by previous workers have been resolved. The observed bands have been classified in terms of Rydberg series.

The behavior of unsteady mixed convection flow of an incompressible viscous fluid over a vertical wedge with constant suction/injection have been investigated. The unsteadiness is due to the time-dependent free stream velocity. The governing boundary layer equations along with the boundary conditions are first converted into dimensionless form by a non-similar transformation, and then resulting system of coupled non-linear partial differential equations is solved by an implicit finite-difference scheme in combination with the quasi-linearization technique. Numerical results for the effects of various parameters on velocity, temperature and concentration profiles and on their gradient at the wall are reported in the present study. The buoyancy force causes considerable velocity overshoot for low Prandtl number (Pr) fluids. Skin friction coefficient, heat and concentration transfer rates are found to alter significantly due to injection/suction for both accelerating and decelerating flow.

Unsteady mixed convection flow over a rotating vertical slender cylinder under the combined effects of buoyancy force and thermal diffusion with injection/suction has been studied where the slender cylinder is inline with the flow. The effect of surface curvature is also taken into account, especially for the applications such as wire and fiber drawing, where accurate predictions are desired. The governing boundary layer equations along with the boundary conditions are first converted into dimensionless form by a non-similar transformation, and then resulting system of coupled nonlinear partial differential equations is solved by an implicit finite difference scheme in combination with the quasi-linearization technique. The effects of various parameters on velocity and temperature profiles and on skin friction coefficients and heat transfer rate at the wall are reported in the present study. � 2007 Elsevier Ltd. All rights reserved.

A general analysis has been developed to study fluid flow and heat transfer characteristics for mixed convection along a rotating vertical slender cylinder. Transformed set of coupled non-linear partial differential equations is solved by an implicit finite difference scheme in combination with the quasilinearisation technique. The effects of rotational, buoyancy and suction/injection parameters have been investigated in the present study. The effects of various parameters on the velocity profiles in x- and ?-directions and the temperature profile are reported in the present study. The buoyancy force causes considerable velocity overshoot for low Prandtl number (Pr) fluids. The Prandtl number (Pr) strongly affects the surface heat transfer rate. Numerical results are presented for the skin friction coefficients in x- and ?-directions and for the Nusselt number. � 2007 Elsevier Ltd. All rights reserved.

Herein, we demonstrate enhancement in photoluminescence (PL) efficiency of InAs submonolayer quantum dots (QDs) resulting from high-energy proton implantation. To obtain optimum energy of protons, we initially varied the energy from 2 MeV to 4.5 MeV at a fixed fluence of 2 x 10(12) ions/cm(2). At an optimum energy of 2.5 MeV, we varied the proton dose from 8 x 10(11) to 1 x 10(13) ions/cm(2) to obtain the best PL response. As compared to the as-grown sample, all implanted samples exhibited PL enhancement, attributed to passivation of non-radiative recombination centers and annihilation of defects, with a consistent blue shift, attributed to out-diffusion of In atoms from the dots. From the PL results, a model was proposed for explaining the material improvement of implanted submonolayer QDs. All samples exhibited significant enhancement in thermal activation energies, confirming that proton implantation improved material quality. Finally, MESA-shaped single-pixel N-i-N detectors were fabricated for both as-grown and optimized samples (implanted with dose of 5 x 10(12) ions/cm(2) at an energy of 2.5 MeV) to measure the temperature-dependent dark current variation. At a temperature of 77 K and a bias of -0.20 V, the dark current density of similar to 4.5 x 10(-4) A/cm(2) of as-grown device was suppressed by more than one order to 6 x 10(-6) A/cm(2) for the optimized sample. (C) 2015 Elsevier B.V. All rights reserved.

A high-resolution (0.003 cm−1) infrared absorption spectrum of the first overtone of the fundamental mode ν8 of methylene fluoride (CH2F2) has been measured on a Bruker IFS 120-HR Fourier transform infrared spectrometer. More than 2000 ro-vibration transitions in the range of 2770–2900 cm−1 with J ⩽ 45 and Ka ⩽ 20 have been assigned in this B-type band centered at 2838.5 cm−1. Precise value for the band origin (2838.579799 cm−1) and centrifugal distortion constants up to third order (ΦJK, ΦKJ, and ΦK) have been obtained by fitting a total of 1474 unblended ro-vibration transitions (J ⩽ 45 and Ka ⩽ 13) of the 2ν8 band with a standard deviation of 0.00029 cm−1 using a Watson’s A-reduced Hamiltonian in the Ir representation. Signature of perturbations with nearby states has been seen.

A high resolution vacuum ultraviolet (HRVUV) beamline based on a 6.65 meter off-plane Eagle spectrometer is in operation at the Indus-1 synchrotron radiation source, RRCAT, Indore, India. To facilitate position sensitive detection and fast spectral recording, a new BaFBr:Eu2+ phosphor based image plate (IP) detection system interchangeable with the existing photomultiplier (PMT) scanning system has been installed on this beamline. VUV photoabsorption studies on Xe, O2, N2O and SO2 are carried out to evaluate the performance of the IP detection system. An FWHM of ~ 0.5 {\AA} is achieved for the Xe atomic line at 1469.6 {\AA}. Reproducibility of spectra is found to be within the experimental resolution. Compared to the PMT scanning system, the IP shows several advantages in terms of sensitivity, recording time and S/N ratio, which are highlighted in the paper. This is the first report of incorporation of an IP detection system in a VUV beamline using synchrotron radiation. Commissioning of the new detection system is expected to greatly enhance the utilization of the HRVUV beamline as a number of spectroscopic experiments which require fast recording times combined with a good signal to noise ratio are now feasible., Comment: Accepted in NIM-A

The effect of low energy H – ions implantation on the InAs/GaAs quantum dot infrared photodetectors had been studied. Light ion implantation was found to be an effective post growth technique which helped dark current density suppression by four orders in the implanted devices. In this study we had mainly concentrated on determining how the defect-related material and structural changes had an impact on dark current density reduction for InAs/GaAs quantum dot infrared photodetectors.

Graphical abstract: - Abstract: Here we propose a carrier transport mechanism for low energy H{sup −} ions implanted InAs/GaAs quantum dot infrared photodetectors supportive of the experimental results obtained. Dark current density suppression of up to four orders was observed in the implanted quantum dot infrared photodetectors, which further demonstrates that they are effectively operational. We concentrated on determining how defect-related material and structural changes attributed to implantation helped in dark current density reduction for InAs/GaAs quantum dot infrared photodetectors. This is the first study to report the electrical carrier transport mechanism of H{sup −} ion-implanted InAs/GaAs quantum dot infrared photodetectors.

A comprehensive analysis of theoretical multiplet splittings and intensities of the fine structure components of the Q(1)(0)H(2) + S(0)(0)N(2) transition in a solid parahydrogen crystal is presented. The consideration of higher order anisotropic term responsible for splittings is essential to explain the observed splitting of the three components. The pair interaction parameters DeltaB and DeltaC have been determined by comparing the theoretical splittings with the experimental values. The information about the small splittings (approximately 0.1 cm(-1)) due to crystal-field interaction is completely obscured due to fast hopping of v(') = 1, J(') = 0 H(2) vibron. Also, the theoretical expressions are derived for the intensities of the fine structure components of the Q(v(H(2)))(0) + S(v(N(2)))(0) transition and the theoretical results are compared with the experimental findings.

The development of unsteady mixed convection flow of an incompressible laminar viscous fluid over a vertical cone has been investigated when the fluid in the external stream is set into motion impulsively, and at the same time the surface temperature is suddenly changed from its ambient temperature. The problem is formulated in such a way that at t = 0, it reduces to Rayleigh type of equation and as t ? ?, it tends to Falkner-Skan type of equation. The scale of time has been selected such that the traditional infinite region of integration become finite which significantly reduce the computational time. The coupled non-linear partial differential equations governing the unsteady mixed convection flow have been solved numerically by using an implicit finite-difference scheme in combination with the quasi-linearization technique. There is a smooth transition from the initial steady state to the final steady state. The velocity, temperature, and concentration profiles and their gradients at the surface for various values of the governing parameters are reported in the present study. � 2006 Elsevier Ltd. All rights reserved.

The electronic absorption spectrum of diiodomethane in the 30 000–95 000 cm−1 region is investigated using synchrotron radiation; the spectrum in the 50 000–66 500 cm−1 region is reported for the first time. The absorption bands in the 30 000–50 000 cm−1 region are attributed to valence transitions, while the vacuum ultraviolet (VUV) spectrum (50 000–95 000 cm−1) is dominated by several Rydberg series converging to the first four ionization potentials of CH2I2 at 9.46, 9.76, 10.21, and 10.56 eV corresponding to the removal of an electron from the outermost 3b2, 2b1, 1a2, and 4a1 non-bonding orbitals, respectively. Rydberg series of ns, np, and nd type converging to each of the four ionization potentials are assigned based on a quantum defect analysis. Time dependent density functional theory calculations of excited states support the analysis and help in interpretation of the Rydberg and valence nature of observed transitions. Density functional theory calculations of the neutral and ionic ground state geometries and vibrational frequencies are used to assign the observed vibronic structure. Vibronic features accompanying the Rydberg series are mainly due to excitation of the C-I symmetric stretch (ν3) and CH2 wag (ν8) modes, with smaller contributions from the C-H symmetric stretch (ν1). UV absorption bands are assigned to low lying valence states 11B2, 11B1, 21A1, 31A1, 21B1, and 21B2 and the unusually high underlying intensity in parts of the VUV spectrum is attributed to valence states with high oscillator strength. This is the first report of a comprehensive Rydberg series and vibronic analysis of the VUV absorption spectrum of CH2I2 in the 50 000–85 000 cm−1 region. The VUV absorption spectrum of CD2I2 which serves to verify and consolidate spectral assignments is also reported here for the first time.

A paper entitled ‘The vacuum ultraviolet absorption spectrum of diatomic calcium’ was published earlier in this journal. It is our opinion that the spectra observed belong to doubly excited transitions of the calcium atom rather than to the calcium dimer. Our observations in this regard are recorded.

In(Ga)As/GaAs-based quantum dot infrared photodetectors (QDIPs) have emerged as one of the most suitable devices for infrared detection. However, quantum dot devices suffer from lower efficiencies due to a low fill-factor (similar to 20%-25%) of dots. Here, we report a post-growth technique for improving the QDIP performance using low energy light ion (H-) implantation. At high bias, there is evidence of suppression in the field-assisted tunneling component of the dark current. Enhancement in peak detectivity (D*), a measure of the signal-to-noise ratio, by more than one order, from similar to 10(9) to 2.44 x 10(10) cm Hz(1/2)/W was obtained from the implanted devices. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4791675]

A comprehensive analysis of theoretical multiplet splittings and intensities of the fine structure components of the Q1(0)H2+S0(0)N2 transition in a solid parahydrogen crystal is presented. The consideration of higher order anisotropic term responsible for splittings is essential to explain the observed splitting of the three components. The pair interaction parameters ΔB and ΔC have been determined by comparing the theoretical splittings with the experimental values. The information about the small splittings (∼0.1 cm−1) due to crystal-field interaction is completely obscured due to fast hopping of v′=1, J′=0 H2 vibron. Also, the theoretical expressions are derived for the intensities of the fine structure components of the QvH2(0)+SvN2(0) transition and the theoretical results are compared with the experimental findings.

The 6 MV Folded Tandem Ion Accelerator (FOTIA) Facility at the Nuclear Physics Division, BARC is operational and accelerated beams of both light and heavy ions are being used extensively for basic and applied research. An average vacuum of the order of 10?8?10?9 Torr is maintained for maximum beam transmission and minimum beam energy spreads. The FOTIA vacuum system comprises of about 55 meter long, 100 mm diameter beam lines including various diagnostic devices, two accelerating tubes and four narrow vacuum chambers. The cross sections of the vacuum chambers are 14mm ? 24mm for 180?, 38mm ? 60mm and 19 ? 44 mm for the and 70? & 90? bending magnets and Switching chambers respectively. All the beam line components are UHV compatible, fabricated from stainless steel 304L grade material fitted with metal gaskets. The total volume ~5.8 ? 105 cm3 and surface area of 4.6 ? 104 cm2, interspersed with total 18 pumping stations. The accelerating tubes are subjected to very high voltage gradient, 20.4 kV/cm, which requires a hydrocarbon free and clean vacuum for smooth operation of the accelerator. Vacuum interlocks are provided to various devices for safe operation of the accelerator. Specially designed sputter ion pumps for higher environmental pressure of 8 atmospheres are used to pump the accelerating tubes and the vacuum chamber for the 180? bending magnet. Fast acting valves are provided for isolating main accelerator against accidental air rush from rest of the beam lines. All the vacuum readings are displayed locally and are also available remotely through computer interface to the Control Room. Vacuum system details are described in this paper.