Search results for "Rotational transition"
showing 5 items of 25 documents
A direct study of the vibrational bending effect in line mixing: The hot degenerate 1110 ← 0110 transition of CO2
1997
Abstract The study of the isotropiv Raman Q -branch of a hot band Π ← Π allows one to establish a direct connection between the vibration-rotation angular momentum coupling and the resulting spectra. Due to the l -doubling, the Q -branch is split into two subbranches characterized by either even or odd rotational quantum number j . The vibrational bending reduces the rotational transfer rates inside each of these subbranches by a factor of about two and induces an inter-subbranch coupling. The expected propensity rule towards conservation of the parity index for high rotational levels is well observed. Calculated spectra are in excellent agreement with CARS experiments for the v 1 + v 2 ← v…
Drops of3Heatoms with good angular-momentum quantum numbers
2000
The stability of drops made of ${}^{3}\mathrm{He}$ atoms is studied by means of a Monte Carlo variational method using wave functions with good angular momentum quantum numbers. The number of constituents considered is in the range 34--40. It is found that the minimal bound drop requires 35 atoms (perhaps 34) and that the preferred wave function must have the maximum spin.
Rotational quenching of monodeuterated water by hydrogen molecules
2011
Cross sections and rate coefficients for low lying rotational transitions in HDO induced by para and ortho-H(2) collisions are presented for the first time. Calculations have been performed at the close-coupling and coupled-states levels with the deuterated variant of the H(2)O-H(2) interaction potential of Valiron et al. [J. Chem. Phys., 2008, 129, 134306]. Rate coefficients are presented for temperatures between 5 and 100 K and are compared to the corresponding rates for H(2)O and D(2)O. Significant differences caused by the isotopic substitution, in particular the C(2v) symmetry breaking, are observed. Finally, our rates are found to be significantly larger (by up to three orders of magn…
STUDIES OF STRUCTURE AND DYNAMICS OF SOLID POLYMERS BY ELASTIC AND INELASTIC NEUTRON SCATTERING
1979
Neutron scattering methods can be applied to solid polymers in order to investigate the structure of the bulk material as well as the nature of the molecular motion. A review of some recently performed studies is presented. Diffusional motion in crystals of chain molecules has been studied by means of quasielastic scattering for the case of n-C33H68 as an example for the relationship between structure and molecular motion. It can be shown that below the so-called rotational transition the paraffin crystals exhibit two types of molecular motion: a translational jump (τt = 0.5 10-8s) and a 180°-rotational jump (τr = 2.5 10-8s). The low frequency vibrations in n-alkanes as models of polyethyle…
Rotational collisional line broadening at high temperatures in the N2 fundamental Q-branch studied with stimulated Raman spectroscopy
1986
Self broadened N 2 Q-branch spectra are measured by high resolution stimulated Raman spectroscopy in the pressure region 0.25-1.9 atm. and in the temperature range 295-1310 K. Non additivity of the Q(J) components due to line overlap arising in the highest pressure range explored is carefully taken into account. Excellent fit of the whole spectra is thus obtained for each pressure with linearly density-dependent line widths. Semi-classical calculations of the line-broadening coefficients lead to consistent values with all the measured ones. These calculations are extended to higher J values and to higher temperatures (up to 2500 K). At last, a simple phenomenological model based on a polyno…