Effect of rotational relaxation on the yield of the multiphoton dissociation of CF3Cl and CF3Br under TEA-CO2 laser pulses

The yield of the multiphoton dissociation of CF₃Cl and CF₃Br induced by TEA-CO₂ laser pulses has been studied in the pressure range between 0.25 and 8 Torr, the laser wavelength being chosen so as to excite preferentially the minor isotopic components¹³CF₃Cl and¹³CF₃Br. For both compounds the dissociation probability is found either to increase almost linearly or to decrease monotonously with gas pressure, according as the laser beam is focused or unfocused, respectively. This behaviour is explained by rotational relaxation effects, and a value of 22ns·Torr for the rotational self-relaxation time of CF₃Cl is obtained.     

Normal and wavelength-modulated absorption of thallium bromide solutions

New results on the absorption spectra of Tl ions in aqueous and alcoholic solutions of TlBr are reported and compared with spectra of Tl ions in single KBr crystals. We study the Tl absorption bands under different conditions and we show that the A-band can be attributed to Tl-Br complexes. The energy parameters of these complexes in alcoholic solutions are given.     

A far-infrared investigation of cathodochromic sodalite

Sodalite absorption bands in the 50–350 cm⁻¹ region were studied using Fourier transform spectroscopy. Vibrational modes were identified using chemical substitution, H₂ and vacuum-annealing, and coloration studies. A bromosodalite band at 294 cm⁻¹ was assigned to an Si—O—Al mode based on Ge substitutions for Si. A bromosodalite band at 200 cm⁻¹ is assigned to an Na—cage vibration based on previous H₂annealing studies and chemical substitution of Ge for Si, Ga for Al and Cl and I for Br. A 107 cm⁻¹ band is the Na—Br related vibration, and substitution of 100% Cl for Br moved this band to 111 cm⁻¹, H₂ and vacuum-annealing studies show a correlation between the amount of Br removed from bromosodalite during annealing and the area of the 107 cm⁻¹ band. A band at 68 cm⁻¹ is the Na—Br mode based on 100% substitution of Cl for Br. Coloration studies in the 50–150 cm⁻¹ region show no changes attributable to F-center formation.     

NMR study of both 19F and 205Tl motions in TlZrF5

Spin-lattice relaxation times in the laboratory T_l and rotating frames T_l? for both ¹⁹F and ²⁰⁵Tl nuclei were measured as a function of temperature. Comparison of the temperature dependence of longitudinal NMR relaxation rates of both ¹⁹F and ²⁰⁵Tl suggests that Tl⁺ ions are more mobile than F^? ones at high temperatures. Furthermore Fourier transform experiments show that two kinds of Tl⁺ ion can be distinguished at high temperatures, one of them being more mobile than the other one and probably responsible for the ionic conductivity of this material.     

Nuclear magnetic relaxation of 205Tl in TlClO4 in a rotating frame

The spin-lattice relaxation time T_1ϱ of ²⁰⁵Tl in TlClO₄ has been measured in a rotating frame. It was found that the temperature dependence of T_1ϱ shows three minima due to the cross relaxation and the random modulation of the dipole-dipole interaction between ²⁰⁵Tl and ¹⁷O of natural abundance (0.037%).     

RESONANCE-ENHANCED MULTIPHOTON IONIZATION SPECTRA OF THE HALOGEN ATOMS

The resonance-enhanced multiphoton ionization (REMPI) spectra of atomic chlorine and bromine in the range of 230-245 nm and 250-285 nm were obtained by using REMPI and time of flight (TOF) techniques. There are twenty -six lines for Cl and twenty-three for Br in the spectra, among which five transitions of Cl and four of Br are observed for the first time. These lines are due to transitions from the Cl(3p ²P⁰_3/2, ²P⁰_1/2) and Br(4p²P⁰_3/2, ²P⁰_1/2) states to upper states induced by two-photon excitation. It is found that the Stark shift of different excited states are almost the same, and they are independent of the S, L, and J quantum numbers of the excited state.     

On the XPS spectra of some carbonyl complexes and the effective charge of the metal and ligand atoms

X-ray photoelectron spectra have been recorded for a series of anionic carbonyl complexes, i.e., M(CO)₅X⁻, M = Cr, Mo; X = Cl, Br. The data are used to calculate the atomic charges in the complexes, using previously determined relations between binding energies and charges. As the binding energies for O1s were found to be sensitive to the degree of backbonding, probably because of extensive relaxation, the oxygen charges could only be estimated indirectly, from the condition that the total anionic charge was −1 a.u.     

Conformational equilibria in dihaloheptasilanes X2Si[SiMe(SiMe3)2]2 with X = F,Cl, Br,I: A Raman spectroscopic and quantum chemical DFT study

Equilibrium geometries, stabilities and vibrational wavenumbers for conformers of the dihaloheptasilanes X₂Si[SiMe(SiMe₃)₂]₂ with X = F, Cl, Br and I were calculated at the density functional B3LYP level employing 6‐311G(d) basis sets and SDD pseudopotentials for Br and I. Two spectroscopically distinct low‐energy conformers were located for all four heptasilanes with energy differences of 5.5, 4.7, 1.9 and 1.2 kJ mol⁻¹ for X = F, Cl, Br and I, respectively. Five more conformers were found for difluoroheptasilane and four for X = Cl, Br and I. They all have relative energies larger than 7.5 and up to 17 kJ mol⁻¹ and are negligibly populated at room temperature. Variable temperature solution Raman spectra (−70 to + 100 °C) in a wavenumber range typical for Si Si stretching vibrations (280‐350 cm⁻¹) confirm these results. For X = Br and I, no temperature effects at all could be observed as a very rapid inter‐conversion between the two low‐energy conformers, which is fast even on the time scale of Raman spectroscopy, occurs. For X = Cl, rapid inter‐conversion also occurs, and a third conformer could be detected at higher temperatures (50–100 °C). For X = F, intensity changes with temperature are consistent with the presence of two low‐energy conformers. Copyright © 2007 John Wiley & Sons, Ltd.     

Observation of a πh9/2 ⊗ νi13/2 oblate band in 188Tl

Excited states in ¹⁸⁸Tl have been studied experimentally using the ¹⁵⁷Gd (³⁵Cl, 4n) reaction at a beam energy of 170MeV. A rotational band built on the πh _9/2 ⊗ νi _13/2 configuration with oblate deformation has been established for ¹⁸⁸Tl. Based on the structure systematics of the oblate πh _9/2 ⊗ νi _13/2 bands in the heavier odd-odd Tl nuclei, we have tentatively proposed spin values for the new band in ¹⁸⁸Tl. The πh _9/2 ⊗ νi _13/2 oblate band in ¹⁸⁸Tl shows low-spin signature inversion, and it can be interpreted qualitatively by the two-quasiparticle plus rotor model including a J-dependent p-n residual interaction.     

New far-infrared laser lines from CH3Cl and CH3Br optically pumped with a continuously tunable high pressure CO2 laser

In this paper we report on the detection of new far-infrared laser lines from CH₃Cl and CH₃Br optically pumped with a continuously tunable high pressure CO₂ laser. We found 80 new lines for CH₃Cl and 9 new lines for CH₃Br in the frequency region between 16 cm^–1 and 41 cm^–1, all due to stimulated Raman scattering. For the Raman gain regions bandwidths up to about 700 MHz were found. We also observed high intensity short far-infrared laser pulses of durations in the nanosecond regime.Permanent address: Physics Department, State Pedagogical University, SU-119435 Moscow, USSR     

Observation of signature inversion in the πh9/2?vi13/2 oblate band

High-spin states in ¹⁹⁰Tl have been studied via the ¹⁶⁰Gd(³⁵Cl, 5nγ) reaction. The level scheme, consisting of the πh _9/2⊗vi _13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly assigned to the oblate band in ¹⁹⁰Tl, resulting in low-spin signature inversion in the πh _9/2⊗vi _13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the oblate bands in ^192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including p-n residual interactions.     

Determination of erosion rates with cosmic ray produced36Cl

We present results of the determination of³⁶C1 (T _1/2=3.0·10⁵a) in rock samples produced in situ by cosmic rays and natural radioactivities. These experiments were designed to determine the feasibility of using³⁶Cl for studying erosion processes in calcium rich minerals like limestone or dolomite. The³⁶Cl/Cl ratios in the samples have been determined with accelerator mass spectrometry (AMS) at the Munich accelerator laboratory. A first application is the investigation of the erosion in the last million years in Allchar (Yugoslavia) for the feasibility study of the geochemical²⁰⁵Tl solar neutrino experiment.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday. Supported by DFG     

The Vibrational Spectra of Complexes with Planar Monothiooxamides. IV. The Copper(II) and Copper(I) Complexes of Neutral Monothiooxamides

The new complexes CuX₂(LH₂), CuX₂ (SH₃) (X = Cl, Br), CuX(LH₂), CuX(SH₃) (X = Cl, Br, I), CuX(H₄MTO)₂ (X = Cl, Br), Cul(H₄MTO) and CuX(H₃MMTO)₂ (X = Cl, Br, I), where LH₂ = N.N′-dimethyl-monothiooxamide, SH₃ = N(s)-methylmonothiooxamide, H₄MTO = monothiooxamide and H₃MMTO = N_(o)-methylmonothiooxamide, have been prepared. The complexes were characterized by elemental analyses, conductivity measurements, magnetic moments and spectroscopic (UV/VIS, FT-IR, Laser-Raman) studies. The vibrational analysis of the complexes has been given using NH/ND, CH₃/CD₃ and ⁶³cu/⁶⁵cu isotopic substitutions. The neutral monothiooxamides behave as monodentate ligands in the Cu(I) complexes coordinating through their thioamide sulfur atom. The ligands LH2 and SH₃ act as bidentate chelating agents in the Cu(II) complexes with ligated atoms being the thioamide sulfur and the amide oxygen.     

Theoretical investigations of the local distortion and electron paramagnetic resonance parameter for CdCl2：V^2＋ and CsMgX3：V^2＋（X=Cl,Br） systems

This paper systematically investigates the local distortion and electron paramagnetic resonance (EPR) parameter for CdCl 2 :V 2+ and CsMgX 3 :V 2+ (X=Cl, Br) systems on the basis of the complete energy matrix, in which not only the contributions due to the spin–orbit coupling of the central ions but also that of the ligands are considered. To describe the difference of overlapping between d-orbits and p orbit, two spin–orbit coupling coefficients are introduced. By simulating the crystal field parameter and EPR parameter, the local distortion parameters are studied and the relationships between the EPR parameter and the spin–orbit coupling coefficients as well as divergent parameter are discussed. These results show that the local structures exhibit compression distortion for CdCl 2 :V 2+ and elongation distortions for CsMgX 3 :V 2+ (X=Cl, Br), respectively. It notes that the empirical formula R ≈ R H + (r i-r h )/2 is not suitable for CdCl 2 :V 2+ and CsMgX 3 :V 2+ (X=Cl, Br) systems. The contributions of ligand to spin–orbit coupling interaction cannot be neglected for strong covalent systems, especially for V 2+ doped in CsMgBr 3 :V 2+ .     

Author index

The mean adsorption lifetimes of F, Cl and Br on (100) and (111) Mo surfaces have been obtained from the first order desorption kinetics observed in low converage conditions (θ < 10^?2 of a monolayer) using a pulsed ionic beam method. The mean adsorption lifetimes τ fit a general expression $\text{τ = τ}{}_0\text{exp}\text{(}\text{E}\text{kT}\text{)}$ in a large temperature range (1700–2400 K) allowing the determination of the binding energies E. The main results of this study are (1) the binding energies decrease from F through Br; (2) the binding energies on both (100) and (111) orientations are similar, E(F)～4.65 eV, E(Cl)～4.15 eV, and E(Br)～3.65 eV. These results are discussed and compared with those previously reported on (100) and (111) Nb and W surfaces. The close binding energies of F, Cl and Br on (100) and (111)^?Nb and Mo surfaces suggest that halogens have a different chemisorption behaviour with respect to O and N.     

Low-temperature time-resolved spectroscopy of APb2X5 crystals (A ≡ K, Rb; X ≡ Cl, Br)

The paper reports on a low-temperature (8 K) time-resolved spectroscopic study of excitonic states and radiative relaxation of electronic excitations in undoped APb₂X₅ crystals (A ≡ K, Rb; X ≡ Cl, Br) performed under selective photoexcitation by synchrotron radiation. The study has revealed a variety of channels of radiative relaxation of intrinsic electronic excitations, which should be primarily assigned to specific features of the electronic structure of the crystal.     

Argon matrix Raman and infrared spectra of SF5Cl,SF5Br,and S2F10

Infrared and laser-excited Raman spectra of SF₅Cl, SF₅Br, and S₂F₁₀ have been observed in dilute argon matrices and in the solid phase at 8 K. The first vibrational assignment of the SF₅Br molecule and assignments for the ν(SCl), ν(SBr), and ν(SS) modes in SF₅Cl, SF₅Br, and S₂F₁₀ are presented. The chlorine isotopic components of the SCl stretch in SF₅Cl have been resolved. The Raman spectrum of SF₅Br, which has not been reported previously, is discussed.     

Isotope ratio of Cl NQR spin-lattice relaxation times in 1D hydrogen-bonding system of tetramethylpyrazine-chloranilic acid at high temperatures

The temperature dependences of spin-lattice relaxation time T ₁ of ³⁵Cl and ³⁷Cl NQR were studied for the co-crystal of tetramethylpyrazine (TMP) with chloranilic acid (H₂ca), TMP-H₂ca, in which one-dimensional hydrogen bonding is formed by alternate arrangement of TMP and H₂ca. The isotope ratio ³⁷Cl T ₁ / ³⁵Cl T ₁ was determined to be 1.0 ± 0.1 above ca. 290 K where a steep decrease of spin-lattice relaxation time T ₁ with increasing temperature was observed. In this temperature range it is suggested that the relaxation is originated from the slow fluctuation of electric field gradient (EFG). Beside EFG fluctuation due to the external-charge-density fluctuation, the small angle reorientation of the quantization axis triggered by a proton transfer motion between N...H-O and N-H...O hydrogen bonding states is proposed.     

Microwave observation of 41K79Br and 41K81Br from laser-ablated potassium bromide

The J = 2 ← 1 transitions of the previously unobserved isotopologues ⁴¹K⁷⁹Br and ⁴¹K⁸¹Br have been recorded with a pulsed-nozzle Fourier transform microwave spectrometer, newly combined with a 532 nm laser ablation source. Aspects of the experimental design are described. Rotational and nuclear quadrupole coupling constants are obtained and combined with published results for ³⁹K⁷⁹Br and ³⁹K⁸¹Br to produce a set of isotopically invariant parameters. New rotational transitions of ²³Na^35,37Cl, ³⁹K⁷⁹Br, and ³⁹K¹²⁷I have also been recorded. Excited vibrational states are not observed, indicating efficient cooling of the metal halides following the initial ablation event.