The measurement of “enhanced” L and M X-ray yields from charge-induced studies with protons and1H 2 + ion beams

Earlier work on Charge Induced X-rays (CHIX) was extended to include the X-ray energy region between 0.70 to 4.0 keV. Protons of 700 keV, and¹H ₂ ⁺ ion beams of equivalent proton energies in the range 350–450 keV were used to produce enhanced yields of L and MX-rays from a suitable selection of highly compacted non-conducting samples. Enhancement factors are given and possible applications are mentioned.     

Comparison of four types of gamma- and X-ray detectors for environmental applications in the 10–450 keV energy range

The performance of four types of - and X-ray radiation detectors for environmental applications was evaluated in the 10–450 keV energy range. Two cadmium zinc telluride (CdZnTe) room temperature semiconductor detectors were evaluated along with a cryogenically cooled semiconductor detector and two different types of scintillation detectors. The energy resolution, absolute peak detection efficiency and peak-to-background ratio of each of the detectors were calculated and intercompared. The advantages and disadvantages of environmental applications of each detector, along with their performance results, are summarized.     

Application of “abnormal” X-ray yields from primary targets of compounds in XSQR studies with proton and alpha particle beams

Previous reports on abnormal yields from charge induced X-ray studies (CHIX) have demonstrated conclusively that such yields are exceptionally high when compared to PIXE at low incident particle energies. A combination of low incident energies and high X-ray yields could be useful for XSQR investigations with low energy accelerators, particularly in studies where the sample matrix swamps the signals from the impurities of interest such as chromium in steels (overwhelming Fe peak) and Cu in brass (high Zn peak). This work discusses the possible applications of CHIX to XSQR studies with primary targets of compressed powders of selected compounds under bombardment with 3000 keV alphas and 800 and 1000 keV protons. A feature of interest in the use of comparatively low beam currents (between 100–150 nA) in the absence of sample cooling. The advantages and limitations of the application are discussed.     

Performance of CdTe detector in the 13–1333 keV energy range

The photopeak efficiency, peak to valley ratio and energy resolution of a 3×3×1 mm³ CdTe detector were determined experimentally for 13–1333 keV photon energy by using polyester coated radioisotopes ²⁴¹Am, ²²Na, ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ¹⁰⁹Cd, ¹³⁷Cs and ¹³³Ba. The data were analyzed by using PX4 from Amptek. The experimental values were fitted to an analytical function of photon energy, and an agreement was observed for the entire range of the studied energies. The results have shown that the CdTe detector has a high performance due to both the improved charge collection efficiency comparable with that of SI GaAs detectors (Vittone et al., 1999), and the low leakage current. Also, CdTe detector is very attractive for field application as it works at room temperature.     

Absolute yields in the fission of 239Pu by mono-energetic neutrons of energy 130–1700 keV

Absolute fission yields of ⁹⁹Mo, ¹¹¹Ag, ¹⁴⁰Ba, ¹⁴⁷Nd and ¹⁵³Sm have been measured for fission of ²³⁹Py by neutrons of energies 130, 300, 700, 900, 1300 and 1700 keV. While yields of ⁹⁹Mo and ¹⁴⁰Ba are constant, those of the other three nuclides increase with energy. This result has implications both for fission theory and for practical applications of fission yields in fast reactors.     

Measurement of L subshell fluorescence yields of some elements in the atomic range 75⩽Z⩽92 using photoionization

L subshell fluorescence yields (ω₁, ω₂ and ω₃) for the elements Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Th and U have been measured at the 123.6 keV γ-ray emission excitation energy from a ⁵⁷Co annular radioactive source (925 MBq) using a Si(Li) detector. The measured L subshell fluorescence yields were compared with the theoretical and semi-empirical values.     

Lι, Lα, Lβ and Lγ X-ray fluorescence cross-sections of heavy elements for the exciting photons energy 38.18, 43.95, 50.21 and 59.5 keV

The cross-sections for the production of L_ι, L_α, L_β and L_γ X-ray fluorescence (XRF) in Er, Ta, W, Au, Hg, Tl, Pb and Bi by photons with energies in the range 38–59.5 keV have been measured, using a standard doublereflection experimental set-up. Measurements have been performed using an annular 241 Am primary source and X-ray emitting secondary-exciter system. Experimental cross-sections have been compared with the theoretically calculated values of L X-ray cross-sections and fairly good agreement is observed between the experimental and theoretical values.     

Photoionization mass spectrometry of gaseous ethene and fluoroethenes in the energy range 280–300 eV

The photoionization mass spectra of the parent cations of ethene, fluoroethene, 1,1′-difluoroethene, cis-difluoroethene, trifluoroethene and tetrafluoroethene have been measured in the energy range 280–300 eV. Below, the C1s ionization limits strong resonances are observed, which are assigned to C(1s) → π^* and C(1s) → R transitions. The term values of the core excited valence states are strongly increased compared to those of π → π^* transitions. The 1s core hole causes negligible shifts in the Rydberg states. Ab initio MRD CI calculations are used to interpret the experimental results.     

The gas-phase and solution mechanism of the isotope exchange reaction OH- + D2 = OD- + HD: Beam study of the solvated-ion reaction OH-. H2O + D2 in the collision energy range 0–2 eV

In a tandem mass spectrometer we have measured the excitation functions (reaction cross section as a function of collision energy) for the following solvated-ion reactant pairs: OH^-.(H₂O) + H₂; OD^-.(D₂O) + D₂; and OH^-.(H₂O) + D₂—in the collision energy range 0–2 eV. Product channels include H₃O^--type production, collision-induced dissociation of reactants and products (OH^- and H^- types) and isotopic mixing. These solvated-ion reactions are used to correlate the reactivity of the isotope exchange reaction OH^- + D₂→OD^- + HD occuring in the gas phase and solution, identifying a proton-transfer mechanism occuring within an H₃O^- intermediate.     

Angle-resolved photoelectron spectra of CF3Br and CF2Br2 in the photon energy range 29–115 eV

Photoelectron asymmetry parameters β and partial photoionization cross sections have been measured for ionization from the molecular orbitals of CF₃Br and CF₂Br₂ using synchrotron radiation in the photon energy range from 19 to 115 eV. Cooper minima are observed in the β spectra for ionizations from orbitals with substantial bromine 4p character. The measured positions of the minima have been compared to the results of non-relativistic calculations performed for different elements of the periodic system. Several shape resonances have been observed in β spectra associated with orbitals of predominantly F(2p) character. Ionization from the Br(3d) subshell has also been observed and studied in some detail. Auger transitions involving 3d electrons have been observed at higher photon energies.     

Calculated energy barriers for the identity SN2 reaction H2O + CH3OH2+ → +H2OCH3 + OH2 in the gas phase,in water clusters,and in aqueous solution

The bimolecular nucleophilic substitution reaction H₂O + CH₃OH₂⁺ → ⁺H₂OCH₃ + OH₂ has been studied using various quantum chemical methods. Accurate barriers for the reaction in the gas phase are presented and discussed. The effect of microsolvation by water molecules in small clusters has been investigated. Extrapolation of the barrier obtained in the small clusters, using a linear relationship between the activation energy and the proton affinity of water clusters, gives a barrier for the reaction in aqueous solution which is in good agreement with that obtained in separate model calculations (polarized continuum model of a super molecule with the first solvation shell included).     

Capture and dissociation in the complex-forming CH + H2 → CH2 + H, CH + H2 reactions

The rate coefficients for the capture process CH + H(2)→ CH(3) and the reactions CH + H(2)→ CH(2) + H (abstraction), CH + H(2) (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH(3) collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems.     

The mechanism and kinetics of energy transfer processes in the Xe–CCl4–M (M=CH4, C2H2, C2H4, C2H6 C3H6 and C3H8) mixtures irradiated by xenon resonance light

The mechanism and kinetics of energy transfer from Xe(6s[3/2]₁) resonance state (E=8.44 eV) to selected hydrocarbon molecules have been investigated by XeCl(B–X) (λ_max=308 nm) fluorescence intensity measurements at stationary conditions in Xe–CCl₄–M systems. Steady-state analysis of the fluorescence intensity dependence on the xenon and M pressure at constant CCl₄ concentration shows that these process occur in the two- and three-body reactions: Xe(6s[3/2]₁⁰)+M→products, Xe(6s[3/2]₁⁰+M+Xe→products. The two- and three-body rate constants for these reactions have been found (see Table 1Table 1. Experimental parameters of Eq. (8)found by least square method in Xe–CCl₄–C₂H₂ and Xe–CCl₄–C₂H₄ systems for chosen xenon pressures in the range 25–150 Torr. Linear correlation coefficients (R) are also shown     

16.

A comparison between the potential energy curves for the X1Σg+ state of H2 and D2     

《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1989,45(8):869-875

The electronic potential for the ground state of H₂ and D₂, molecules has been calculated from spectroscopic molecular constants. Numerical integration of the radial wave equation gives accurate self-consistent values (an eigenvalue mean deviation of about 1 cm⁻¹). A comparison between different potentials is reported.     

17.

Synthesis and structure of 1-benzyl-5-amino-1H-tetrazole in the solid state and in solution: Combining X-ray diffraction, 1H NMR,FT–IR,and UV–Vis spectra and DFT calculations     

《Comptes Rendus Chimie》2015,18(4):422-429

Compound 1-benzyl-5-amino-1H-tetrazole (BAT) was synthesized and characterized by ¹H NMR, FT–IR, and UV–Vis spectroscopies and elemental (CHNS) analysis. The crystal structure was further elucidated by single-crystal X-ray diffraction. Density functional theory (DFT) calculations with B3LYP and PBE1PBE functionals of the BAT were performed to provide structural and spectroscopic information and guide spectral assignments. The compound crystallizes in monoclinic primitive system space group P2(1)/c with a = 14.91 Å, b = 5.12 Å, c = 11.19 Å, V = 852 Å³, Z = 4, R₁ = 0.0428 at 298 K. The structure exhibits intermolecular hydrogen bonds of the type N–H(amino)···N(tetrazole). Simultaneous hydrogen bonds between amino···tetrazole and tetrazole···amino establish a dimeric intermolecular structure, whereas another hydrogen bond between the remaining H atom of the amino group and the other N atoms of the tetrazole ring extends the structure into another dimension. The crystal structure of BAT is properly reproduced by DFT calculations only when a dimeric or tetrameric model is employed in the modeling. Comparisons between experimental and calculated spectral properties suggest that the monomeric form of BAT is dominant in aprotic, polar, hydrogen-bonding solvents, such as DMSO and DMF.     

18.

Alignment of Ar+ (2p −1 2 P 3/2) ions after electron impact ionisation in the range 1 keV to 268 eV     

W. Weber  R. Huster  M. Kamm  W. Mehlhorn 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,22(1):419-424

We have measured the alignmentA ₂₀ of Ar⁺(2p ^{?1 2} P _3/2) ions after electron impact ionization in the range of primary electron energyE ₀=1000...268 eV (range of excess energyE ₁=750...19.5 eV) via the anisotropic angular distribution ofL ₃?M _2,3 M _2,3(¹ S ₀) Auger electrons. On decomposing the Auger spectra into their components special care was taken by including the effect of the postcollision interaction on the shape of Auger lines. The present alignment values forE ₀≧350 eV agree well with previously existing experimental values of DuBois and Rodbro and with theoretical DWBA results of Berezkho and Kabachnik, but forE ₀<350 eV they deviate systematically from the DWBA values. For the lowest impact energyE ₀, which is only 19.5 eV above threshold, we obtainedA ₂₀=+0.09(16). This value clearly indicates that in the ionisation process near threshold the two low-energy electrons escape not only with a two-electron partial waveL=0, according to Wannier's original assumption, but also with partial wavesL>0.     

19.

Spectroscopy of H 3 + with energies above the barrier to linearity: rovibrational transitions in the range of 10,000–14,000 cm−1     

Ralph Jaquet 《Theoretical chemistry accounts》2010,127(3):157-173

Based on a recently extended potential energy surface for H ₃ ⁺ with a highly reliable form of the topology of the surface far beyond the barrier to linearity, rovibrational frequencies in the range of 10,000–14,000 cm^?1 have been derived and are compared with new experiments. The computed transition frequencies reproduce experimental transitions mostly within a few tenths of a wavenumber, if non-adiabatic effects are crudely simulated using different reduced masses for vibrational and rotational motions. Deviations can only be compensated if non-adiabatic effects are treated more rigorously.     

20.

Disruptive influence of the host cage C60 on the guest He–H+ bond and bonding in H3+     

《印度化学会志》2021,98(8):100101

Although a helium atom prefers to stay at the centre of a fullerene (C₆₀) cage and a proton binds with one of the carbon atoms from inside, DFT(MN15)/cc-pVTZ and DLPNO-MP2/def2-TZVP calculations show that the helium atom and the proton in HeH⁺ prefer to stay away from the centre of the cage, weakening the He–H⁺ covalent bond considerably. Both the helium atom and the proton exhibit noncovalent interactions with the carbon atoms of two pentagons at the opposite ends of the fullerene cage. Our calculations also show that a linear arrangement of H₃⁺ (inside C₆₀), pointing towards the centres of two pentagons opposite to each other, with the proton breaking away from H_2, is energetically more favored over the equilateral triangle geometry of free H₃⁺.     

A comparison between the potential energy curves for the X1Σg+ state of H2 and D2

The electronic potential for the ground state of H₂ and D₂, molecules has been calculated from spectroscopic molecular constants. Numerical integration of the radial wave equation gives accurate self-consistent values (an eigenvalue mean deviation of about 1 cm⁻¹). A comparison between different potentials is reported.     

Synthesis and structure of 1-benzyl-5-amino-1H-tetrazole in the solid state and in solution: Combining X-ray diffraction, 1H NMR,FT–IR,and UV–Vis spectra and DFT calculations

Compound 1-benzyl-5-amino-1H-tetrazole (BAT) was synthesized and characterized by ¹H NMR, FT–IR, and UV–Vis spectroscopies and elemental (CHNS) analysis. The crystal structure was further elucidated by single-crystal X-ray diffraction. Density functional theory (DFT) calculations with B3LYP and PBE1PBE functionals of the BAT were performed to provide structural and spectroscopic information and guide spectral assignments. The compound crystallizes in monoclinic primitive system space group P2(1)/c with a = 14.91 Å, b = 5.12 Å, c = 11.19 Å, V = 852 Å³, Z = 4, R₁ = 0.0428 at 298 K. The structure exhibits intermolecular hydrogen bonds of the type N–H(amino)···N(tetrazole). Simultaneous hydrogen bonds between amino···tetrazole and tetrazole···amino establish a dimeric intermolecular structure, whereas another hydrogen bond between the remaining H atom of the amino group and the other N atoms of the tetrazole ring extends the structure into another dimension. The crystal structure of BAT is properly reproduced by DFT calculations only when a dimeric or tetrameric model is employed in the modeling. Comparisons between experimental and calculated spectral properties suggest that the monomeric form of BAT is dominant in aprotic, polar, hydrogen-bonding solvents, such as DMSO and DMF.     

Alignment of Ar+ (2p −1 2 P 3/2) ions after electron impact ionisation in the range 1 keV to 268 eV

We have measured the alignmentA ₂₀ of Ar⁺(2p ^{?1 2} P _3/2) ions after electron impact ionization in the range of primary electron energyE ₀=1000...268 eV (range of excess energyE ₁=750...19.5 eV) via the anisotropic angular distribution ofL ₃?M _2,3 M _2,3(¹ S ₀) Auger electrons. On decomposing the Auger spectra into their components special care was taken by including the effect of the postcollision interaction on the shape of Auger lines. The present alignment values forE ₀≧350 eV agree well with previously existing experimental values of DuBois and Rodbro and with theoretical DWBA results of Berezkho and Kabachnik, but forE ₀<350 eV they deviate systematically from the DWBA values. For the lowest impact energyE ₀, which is only 19.5 eV above threshold, we obtainedA ₂₀=+0.09(16). This value clearly indicates that in the ionisation process near threshold the two low-energy electrons escape not only with a two-electron partial waveL=0, according to Wannier's original assumption, but also with partial wavesL>0.     

Spectroscopy of H 3 + with energies above the barrier to linearity: rovibrational transitions in the range of 10,000–14,000 cm−1

Based on a recently extended potential energy surface for H ₃ ⁺ with a highly reliable form of the topology of the surface far beyond the barrier to linearity, rovibrational frequencies in the range of 10,000–14,000 cm^?1 have been derived and are compared with new experiments. The computed transition frequencies reproduce experimental transitions mostly within a few tenths of a wavenumber, if non-adiabatic effects are crudely simulated using different reduced masses for vibrational and rotational motions. Deviations can only be compensated if non-adiabatic effects are treated more rigorously.     

Disruptive influence of the host cage C60 on the guest He–H+ bond and bonding in H3+

Although a helium atom prefers to stay at the centre of a fullerene (C₆₀) cage and a proton binds with one of the carbon atoms from inside, DFT(MN15)/cc-pVTZ and DLPNO-MP2/def2-TZVP calculations show that the helium atom and the proton in HeH⁺ prefer to stay away from the centre of the cage, weakening the He–H⁺ covalent bond considerably. Both the helium atom and the proton exhibit noncovalent interactions with the carbon atoms of two pentagons at the opposite ends of the fullerene cage. Our calculations also show that a linear arrangement of H₃⁺ (inside C₆₀), pointing towards the centres of two pentagons opposite to each other, with the proton breaking away from H_2, is energetically more favored over the equilateral triangle geometry of free H₃⁺.