Ch-stretching gas phase overtone spectrum of symmetric neopentane-d4

The overtone spectrum of neopentane-d₄, C(CH₂D)₄, is examined and the local mode model is used to assign the prominent peaks. Proposed coupling routes for intramolecular vibrational relaxation of CH-stretching overtones are discussed. The dominant vibrational relaxation pathway is identified by comparisons of neopentane-d₄, neopentane and benzene overtone bandwidths.     

Vibrational relaxation of CF4 at low temperatures

An apparatus for low temperature acoustic measurements is described. The vibrational relaxation times of CF₄ have been determined between 183 K and 295 K, and the mechanism of vibrational energy transfer in this molecule is discussed.     

Brillouin scattering in liquid mixtures: CCl4/CHCl3

The Brillouin light scattering spectra of mixtures of liquid CCl₄ and CHCl₃ have been obtained. The resulting relaxation rates and the relaxing energy reservoir were studied as a function of the mole fraction over the entire concentration range. The energy exchange between the pertinent degrees of freedom are discussed in terms of the relaxation rates of homomolecular and heteromolecular collisions. We came to the conclusion that the resonance energy transfer between vibrational levels play a significant role in determining the vibration—translation energy migration observed by Brillouin scattering'     

Photoacoustic study of vibration to translation-rotation transfer inch4 and cd4

The vibrational deactivation of CH₄ and CD₄ is studied experimentally in the gas phase using the photoacoustic method. Excitations of v₄ and v₃ modes are performed. The corresponding kinetic models are established using the fact that vibration-to-vibrati transfers are very efficient and hold the adjacent vibrational levels in a quasi-equilibrium distribution. The models are tested between 140 and 376 K and the vibration to translation-rotation rate constants are determined in pure CH₄ pure CD₄, and CH₄-CD₄ mixtures.     

Infrared spectra of KNaSO4 and K3Na(SO4)2

The infrared spectra, transmittance and polarized reflectance, of KNaSO₄ and K₃Na(SO₄)₂ are reported. Group theoretical analysis was carried out and a vibrational assignment proposed on basis of C_3v and D_3d symmetries. Factor group and site effects are discussed.     

Vibrational relaxation in SnCl4

The vibrational relaxation in liquid SnCl₄ was determined as a function of temperature. Comparison of theory and experiment leads to the conclusion of a simultaneous relaxation of three internal modes.     

Vibrational relaxation in SO2

SSH—Tanczos calculations are carried out to estimate the energy transfer probabilities and the slow vibrational relaxation time in SO₂ in the temperature range 300–2000 K. The theoretical results suggest a series process below 1000 K, and a complex series/parallel process above that temperature for the vibrational relaxation in SO₂. The theoretical results are compared with the known experimental data.     

Vibrational relaxation of N2(A3Σu+,υ = 1, 2,3) by CH4 and CF4

N₂(A, υ = 0-3) produced by the Ar(³P_0,2) + N₂ reaction and detected by laser-induced fluorescence undergoes rapid, stepwise vibrational relaxation but slow electronic quenching with added CH₄ or CF₄. Rate constants, k_Q^υ, of 1.5, 3.1, and 5.0 × 10^?12 cm³ s^?1 are measured for Q = CH₄, υ = 1-3, and 0.47, 1.8, and 5.5 × 10^?12 cm³ s^?1 for Q = CF₄, υ = 1-3, with ≈±20% accuracy (1σ). Information is also obtained for the unrelaxed, relative υ populations.     

Vibrational relaxation of compressed nD2 fluid

Experimental observations of the vibrational population relaxation time of ⁿD₂ fluid under pressures of up to 500 atm in the 25–85 K range are presented and described in terms of a semi-classical model for energy transfer in liquids. For comparison with the parameters of this model, a classical equivalent potential for quantum systems is derived from the “real” intermolecular potential.     

Vibrational relaxation of CO2(v3) by O atoms

The vibrational relaxation time for CO₂(v₃) + O(³P) has been measured by laser fluorescence. The observed value, βCO₂.O = 0.21 ± 0.04 μsec, is an order of magnitude lower than the relaxation time for self-collisions.     

Rotation-vibration-translation energy transfer in laser excited Li2 (B1Πu)

Using the method of laser fluorescence, inelastic collisions with rare gas atoms of electronically excited ⁷Li₂ molecules in the υ = 2 and 4 levels were studied. Vibrational transitions ranging from Δ = +2 to ?4 were observed. The simultaneous rotational transitions were completely resolved, and detailed rate constants k_{Δυ, ΔJ} for specific collision- induced quantum jumps Δυ, ΔJ were determined. The effect of secondary rotational relaxation was eliminated by an extrapolation to zero pressure. By integration over ΔJ, rate constants k_Δυ, were found. They are, within the error limits, independent of the collision partner and on the initial υ (2 or 4) and depend rather weakly on Δυ. These findings are compared with theoretical results from various methods, generally based on a collinear collision model. The apparent disagreement in all respects suggests strongly the importance of rotational degrees of freedom in the collision. Experimental evidence for this is the large amount of V — R transfer observed, which about equals the V — T transfer. The mean cross sections σ(Δυ) for specific vibrational transitions Δυ range between 6 and 15 A², among the largest ever observed.     

Equilibrium structure and vibrational frequencies of the O4 molecule

SCF closed shell calculations were performed to determine the equilibrium structure and vibrational frequencies of the O₄ molecule by means of Payne's method and with the help of the molecule's symmetry coordinates. The equilibrium geometry corresponds to symmetry group D_2d with R = 1.505 Å and h = 0.094 Å. The vibrational frequencies are: ν₅(E) = 885.5 cm^?1, ν₃(B₁) = 1051.9 cm^?1, ν₁(A₁) = 1018.3 cm^?1, ν₄(B₂) = 880.3 cm^?1. The second vibrational coordinate (A₁) corresponds to a double-well potential. The first vibrational levels were calculated by a variational method.     

NMR study of molecular reorientations in NH4H2AsO4

Zeeman (T_1Z) and dipolar (T_1D) spin-lattice relaxation times of protons in NH₄H₂AsO₄ were measured as a function of temperature. The existence of a slow motion (τ ≈ 10^?3 see) is established, which is most probably a low frequency hindered reorientation of H₂AsO₄ groups. This motion is slowed down below the Curie point T_c. A sharp increase of the dipolar relaxation rate above T = 314°K indicates the possibility of a new high temperature phase transition in this compound.     

Energy transfer in reactive and nonreactive collisions of Na with Na2

Stimulated by the experimental finding of vibrationally and rotationally cold dimers in supersonic nozzle molecular beams of sodium, we have studied energy transfer in collisions of Na with Na₂ over a wide range of initial relative translation energies E and impact parameters b by a classical mechanical trajectory method. The vibrational and rotational energies were initialized using Boltzmann distributions characterized by temperatures T_vib = 150 K, T_rot = 50 K. We find that for large values of E the energy transfer in reactive collisions increases with b while it decreases with b for the nonreactive collisions. For low values of E, energy transfer is a decreasing function of b for both reactive and nonreactive encounters. Both the reactive and nonreactive mechanisms are very efficient in effecting transfer, between 40–70% of the initial relative translational energy is converted into internal energy of the diatom, leading to the conclusion that the reverse collisions would result in the rapid relaxation observed in experiment.     

Mode-to-mode vibrational energy transfer in D2CO: Evidence of coriolis-enhanced rotational selectivity

Infrared—ultraviolet double resonance spectroscopy is used to demonstrate rapid collision-induced V-V transfer between the v₆ and v₄ vibrational manifolds of D₂CO. The rate of transfer is at least gas-kinetic and is explained in terms of Coriolis coupling and rotationally specific, quasi-resonant relaxation channels     

Low-temperature absorption spectra of the MoO2−4 ion in Cs2SO4 and of the ReO−4 ion in RbClO4 and in (C2H5)4NClO4

Absorption spectra of single crystals of Cs₂SO₄ doped with MoO^2?₄ and of RbClO₄ and (C₂H₅)₄HClO₄ doped with ReO^?₄ have been measured at the liquid-helium temperature. All spectra show two band systems with pronounced vibrational structures. In T_d symmetry they must correspond to ¹T₂ - ¹A₁ charge-transfer electornic transitions. It is likely that in the two band systems there are more than two electronic transitions.     

Sensitization of the OH(A 2Σ+ → X 2Πi) emission by Hg(6 3P0) metastables

The electronic energy transfer process Hg(6 ³P₀) + OH(X²Π_i, υ = 0,K) → Hg(6 ¹S₀) + OH(A ²Σ⁺, υ,K) has been studied by the sensitized fluorescence method. A rather broad spectrum of rotational population, N_υ′K′, was obtained under conditions of minimum relaxation, which illustrates the non-resonant and non-optical nature of this energy transfer process. The fractions of the exoergicity, above electronic excitation of OH(A ²Σ⁺, υ = 0, K = 0), going into vibrational, rotational and translational excitation are 0.11, 0.31, and 0.58, respectively. A statistical mode of energy partitioning, such as would result from long-lived complex formation, seems to account well for these observations.     

Study of V-V transfer in CD2Cl2 by laser-induced fluorescence experiments

Vibrational energy transfer between the fundamentals of CD₂Cl₂ is studied by laser-induced fluorescence experiments. The data obtained confirm the result and interpretation of former acoustic experiments which indicated an inefficient energy exchange between the lowest vibrational mode and the upper modes. The pτ value obtained for this V-V process is 60 μs Torr. Energy transfer between the upper modes is more efficient and the corresponding pτ values are smaller than 4 μs Torr for the modes investigated in this work.     

Crystal structure and vibrational spectra of tetrasodium dimagnesium dihydrogen diphosphate octahydrate Na4Mg2(H2P2O7)4·8H2O

A tetrasodium dimagnesium dihydrogen diphosphate octahydrate Na₄Mg₂(H₂P₂O₇)₄·8H₂O was synthesized. It crystallizes in the monoclinic system, space group P2₁/m (no. 11), Z=4, and its unit-cell parameters are: a=8.0445(3) Å, b=11.5244(5) Å, c=9.0825(4) Å, β=113.1401(2)°, V=774.28(6) Å³. The structure was determined by single-crystal X-ray diffractometry and refined to a R index of 0.0294 (wR=0.0727) for 1878 independent reflections with I>2σ(I). The framework is made by the alternance of layers of MgO₆/NaO₆ octahedra and double tetrahedra PO₄ along b-axis. Such layers are characterized by the presence of strong hydrogen bonds. (H₂P₂O₇)²⁻ anions exhibit bent eclipsed conformation. Besides, the crystal was analyzed by FT-IR and micro-Raman vibrational spectroscopy. No coincidences of the majority of the Raman and infrared spectra bands of Na₄Mg₂(H₂P₂O₇)₄·8H₂O confirms a centrosymmetric structure of this material. The vibrational spectra confirm the bent POP configuration in this compound.