The effect of kinematic parameters on inelastic scattering of glyoxal

The effect of kinematic parameters (relative velocity v(rel), relative momentum p(rel), and relative energy E(rel)) on the rotational and rovibrational inelastic scatterings of 0(0)K(0)S(1) trans-glyoxal has been investigated by colliding glyoxal seeded in He or Ar with target gases D2, He, or Ne at different scattering angles in crossed supersonic beams. The inelastic spectra for target gases He and D2 acquired with two different sets of kinematic parameters revealed no significant differences. This result shows that kinematic factors have the major influence in the inelastic scattering channel competition whereas the intermolecular potential energy surface plays only a secondary role. The well-defined exponential dependence of relative cross sections on exchanged angular momentum identifies angular momentum as the dominant kinematic factor in collision-induced rotationally and rovibrationally inelastic scatterings. This is supported by the behavior of the relative inelastic cross sections data in a "slope-p(rel)" representation. In this form, the data show a trend nearly independent of the target gas identity. Representations involving E(rel) and v(rel) show trends specific to the target gas.     

Some recent experiments on inelastic electron-molecule collisions at low energies

This work describes a novel trochoidal electron spectrometer and illustrates its properties on a few examples. In the first example vibrational excitation in the small molecules H₂ and N₂ is measured. Comparison of the results with theoretical work points to the neccessity of using non local methods for correct treatment of near-threshold region and of extremely short-lived resonances. In the second example the observation of resonant autodetachment of Feshbach resonances in many organic molecules is reported.     

Simple systematization of vibrational excitation cross-section calculations for resonant electron-molecule scattering in the boomerang and impulse models

Vibrational excitation (nu(f)<--nu(i)) cross-sections sigma(nu(f)<--nu(i) )(E) in resonant e-N(2) and e-H(2) scattering are calculated from transition matrix elements T(nu(f),nu(i) )(E) obtained using Fourier transform of the cross correlation function , where psi(nu(i))(R,t) approximately =e(-iH(A(2))-(R)t/h phi(nu(i))(R) with time evolution under the influence of the resonance anionic Hamiltonian H(A(2) (-))(A(2) (-)=N(2)(-)/H(2) (-)) implemented using Lanczos and fast Fourier transforms. The target (A(2)) vibrational eigenfunctions phi(nu(i))(R) and phi(nu(f))(R) are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curves of the neutral target. Application of this simple systematization to calculate vibrational structure in e-N(2) and e-H(2) scattering cross-sections provides mechanistic insights into features underlying presence/absence of structure in e-N(2) and e-H(2) scattering cross-sections. The results obtained with approximate PE curves are in reasonable agreement with experimental/calculated cross-section profiles, and cross correlation functions provide a simple demarcation between the boomerang and impulse models.     

Mode-selective O-H stretching relaxation in a hydrogen bond studied by ultrafast vibrational spectroscopy

The ultrafast relaxation of the excited O-H stretching vibration is studied by ultrafast infrared-pump/infrared-probe and infrared-pump/Raman-probe spectroscopy. We demonstrate a 200 fs lifetime of the hydrogen-bonded O-H stretching mode in 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole (TINUVIN P). O-H stretching relaxation occurs through a few major channels that all involve combination and overtone bands of modes with considerable in-plane O-H bending character. In particular, the mode, which contains the largest O-H bending contribution, plays a prominent role for primary processes of intramolecular vibrational energy redistribution. Theoretical calculations of vibrational energy transfer rates based on a Fermi golden rule approach account for the experimental findings.     

The Fredholm method in low energy electron-molecule scattering: Static exchange

The Fredholm method using a two-center, L² basis is presented for electron-hydrogen molecule scattering including exchange, but neglecting polarization. At low energies, phase shifts computed by analytically continuing the Fredholm determinant agree well with J = 0 close-coupling results.     

The Born closure approximation for the scattering amplitude of an electron-molecule collision

When the fixed-nuclei (FN) approximation is applied to the calculation of electron scattering from a polar molecule, the resulting cross section diverges in the forward direction of scattering. This is due to the long-range nature of the interaction between the electron and the molecular dipole. To avoid this difficulty, a hybrid method is proposed for the calculation of the scattering amplitude. This method is based on the FN approximation for a close collision and the Born approximation for a distant collision. The present paper describes the detailed formulation of the method for practical applications. Furthermore the present approach is extended to other long-range interactions (due to quadrupole moment and/or polarization effect) and to a dipole-allowed vibrational excitation. In these cases, while no divergence occurs, it is often difficult to confirm the convergence of the partial-wave expansion. With the employment of the present approach, it is much easier to confirm the convergence and hence to obtain reliable cross sections. The formulas are given for diatomic molecules as well as for polyatomic ones. Received: 12 June 2000 / Accepted: 6 July 2000 / Published online: 24 October 2000     

The rotational dependence of purely vibrational anharmonic resonances

Despite the fact that purely vibrational anharmonic resonances are diagonal in all rotational quantum numbers, it is now recognized that there may be a slight rotational dependence of the off-diagonal matrix element and that such dependence has important effects on the vibration-rotation spectrum. The effect has previously been treated empirically and numerical estimates obtained for the J-dependent terms in the Fermi resonances in a number of linear triatomic molecules. The calculation of these J-dependent terms using first-order anharmonic wavefunctions is now described and the results are compared with the experimental values in the cases of CO₂ and CS₂.     

Quantitative relationships between bond lengths,stretching vibrational frequencies,bond force constants,and bond orders in the hydrogen-bonded complexes involving hydrogen halides

To uncover the correlation between the bond length change and the corresponding stretching frequency shift of the proton donor D–H upon hydrogen bond formation, a series of hydrogen-bonded complexes involving HF and HCl which exhibit the characteristics of red-shifted hydrogen bond were investigated at the MP2/aug-cc-pVTZ, M062X/aug-cc-pVTZ, and B3LYP/aug-cc-pVTZ(GD3) levels of theory with CP optimizations. A statistical analysis of these complexes leads to the quantitative illustrations of the relations between bond length and stretching vibrational frequency, between bond length and bond force constant, between stretching vibrational frequency and bond force constant, between bond length and bond order for hydrohalides in a mathematical way, which would provide valuable insights into the explanation of the geometrical and spectroscopic behaviors during hydrogen bond formation.     

Complete assignment of the vibrational modes of C60 by inelastic neutron scattering spectroscopy and periodic-DFT

In this paper we exploit the complementarity of inelastic neutron scattering (INS), infrared and Raman spectroscopies with ab initio calculations to generate an updated assignment of the vibrational modes of C(60). We have carried out periodic-DFT calculations of the high temperature face centred cubic phase modelled as the standard structure and also of the low temperature simple cubic phase, the latter for the first time. Our assignment differs from all previous work, however, it is the only one that is able to successfully reproduce the INS spectrum in terms of both transition energies and intensities. In addition to the INS spectrum we are also able to quantitatively simulate the major features of the infrared and Raman spectra in the high temperature phase and the infrared spectrum in the low temperature phase.     

The vibrational spectra and rotational isomerism of 1,1,1-Trimethoxyethane

The liquid, vapour and solid-state infrared spectra of 1,1,1-trimethoxy-ethane were recorded in the region 250–4000 cm⁻¹. The laser-Raman spectrum with qualitative depolarization data was obtained for liquid only. The spectra show that there are at least two rotational isomers present in the liquid phase. The solution spectra reveal that the less polar form is the more stable in the liquid phase. The form playing an important role has GGG configuration. A vibrational assignment has been attempted for the observed infrared and Raman bands.     

The analytical potential of neutron inelastic scattering reactions

The analytical application of neutrons produced by the⁹Be(d, n)¹⁰B reaction using 3-MeV deuterons is presented. The principal reaction for such neutrons is that of inelastic scattering. Fifteen elements were chosen for study (Se, Br, St, Y, Ag, Cd, In, Sn, Er, Lu, Hf, W, Ir, Au and Hg). Gamma-ray spectra of the metastable isomers produced were obtained with a Ge(Li) detector. The minimum weight of each element detectable (L_D) was then determined from the spectra. Assuming a sample weight of 5g, several elements (Se, Br, Sr, Y, Hf and Au) had L_D values of less than 100 ppm.     

Rotational decoupling of vibrational modes due to rotational excitation: Application to a model of the HDO stretching motions

Rotational motion can have a significant effect on intramolecular vibrational dynamics. In this paper, we explore the recently discovered phenomenon of rotational decoupling through both quantum mechanical and classical methods. It is found in a model system for the stretching motions of HDO, that rotational motion about the c axis can decouple the stretches. This fact can be understood as a cancellation between kinetic and centrifugal coupling as illuminated using classical resonance analysis and quantum matrix element calculations. The significance of this phenomenon is discussed in infrared multiple photon absorption experiments with specific application to isotope separation in HDO.     

The rotational and vibrational spectra of 1,3-dithiole- 2-one

Microwave spectra of 1,3-dithiole-2-one show that the molecule has a planar equilibrium conformation. IR and Raman spectra are analysed to give the normal modes of vibration.     

The inelastic neutron scattering spectrum of chloroform in solution

The incoherent inelastic neutron scattering (INS) spectrum of CHCl₃ in liquid SO₂ (ambient temperature) in the region 0–3600 cm⁻¹ is presented. For the first time it has been demonstrated that good quality INS data on solutes can be obtained over this energy transfer range. A discussion of suitable solvents for further work is included.     

烷基极化效应与X=O键伸缩振动频率

烷基取代物R'X=O的X=O键伸缩振动频率ν与烷基R的极化效应指PEI(R)的关系可表示为:ν=a+bPEI(R)。研究结果表明,烷基的极化效应使X=O键的伸缩振动频率降低。     

The k-j-j' vector correlation in inelastic and reactive scattering

Quasi-classical trajectory (QCT) methods are presented which allow characterization of the angular momentum depolarization of the products of inelastic and reactive scattering. The particular emphasis of the theory is on three-vector correlations, and on the connection with the two-vector correlation between the initial and final angular momenta, j and j', which is amenable to experimental measurement. The formal classical theory is presented, and computational results for NO(A) + He are used to illustrate the type of mechanistic information provided by analysis of the two- and three-vector correlations. The classical j-j' two-vector correlation results are compared with quantum mechanical calculations, and are shown to be in good agreement. The data for NO(A) + He support previous conclusions [M. Brouard, H. Chadwick, Y.-P. Chang, R. Cireasa, C. J. Eyles, A. O. L. Via, N. Screen, F. J. Aoiz, and J. K?os, J. Chem. Phys. 131, 104307 (2009)] that this system is only weakly depolarizing. Furthermore, it is shown that the projection of j along the kinematic apse is nearly conserved for this system under thermal collision energy conditions.     

Vibrational close coupling in the discrete basis set theory of electron-molecule scattering

The theory of low-energy electron-molecule scattering by T-matrix expansion in L² basis orbitals is generalized to include coupling with molecular vibration. A mixed basis set of scattered-electron orbitals and vibrational functions is used. The resulting integrals are shown to be only marginally more difficult than in adiabatic-nuclei theory. Possible shortcuts in the matrix inversion involved are discussed.     

An analytical method for the calculation of the relative intensities of bending and stretching modes in inelastic neutron scattering spectra

An approximate analytical method is presented for calculating the relative intensities of the bands due to the stretching (ν) and doubly degenerate b     

Low frequency skeletal vibrations and rotational isomers of solid 1,4-dibromobutane and 1,5-dibromopentane studied by neutron inelastic scattering

The neutron inelastic spectra of solid 1,4-dibromobutane and 1,5-dibromopentane have been taken at several temperatures. The observed neutron spectra are assigned to the skeletal bending and torsion modes on the basis of normal coordinate calculations, in which only intramolecular valence force fields are used. The spectral assignments are consistent with the GG conformer being the predominant species in solid 1,4-dibromobutane while the TT conformer is predominant in 1,5-dibromopentane; lesser amounts of the TT isomer in the former and the GG isomer in the latter have also been identified.