Collisional effects on the internal and translational energy distributions of laser-excited and thermally heated SF6 supersonic beams
- 15 February 1984
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 80 (4) , 1490-1505
- https://doi.org/10.1063/1.446898
Abstract
Collision induced multiple‐photon absorption by SF6 of cw CO2 laser radition [P(16) 10.6 μm, 8.5 W] has been carried out inside a transparent, capillary, nozzle beam source. Resonant laser excitation of the gas just upstream of the nozzle exit enhances the internal energy by 0.38 eV molecule−1 over its value at Tnz=290 K. In comparison, simple thermal heating of the nozzle to 544 K, which provides a similar velocity distribution in the supersonic beam to that found with laser irradiation, produces a beam enhanced in internal energy by only 0.03 eV molecule−1. Energies were determined using bolometer, mass filter (or flux meter), and time‐of‐flight measurements. Laser excitation in the nozzle induces high vibrational temperatures in the beam which cannot be achieved by simple thermal heating of the nozzle. For an assumed Boltzmann distribution of vibrational energy, the ‘‘vibrational temperature’’ of laser excited SF6 increases (from Tnz=290 K) to Tvib=680 K. Tvib for the thermally heated SF6 is always less than the nozzle temperature. The internal energies measured are lower than those predicted using a free‐jet isenthalpic expansion equation.Keywords
This publication has 64 references indexed in Scilit:
- Competing dissociation channels in the infrared multiphoton decomposition of ethyl vinyl etherThe Journal of Chemical Physics, 1983
- Picosecond infrared double resonance studies on SF6The Journal of Chemical Physics, 1981
- Laser excitation of sulfur hexafluoride in a transparent nozzle beam. Collision-assisted absorption and up-pumpingThe Journal of Physical Chemistry, 1981
- Mode dependent enhanced vibrational relaxation in low energy He–1B2 aniline collisionsThe Journal of Chemical Physics, 1980
- Laser Spectroscopy of Cold Gas-Phase MoleculesAnnual Review of Physical Chemistry, 1980
- Vibrational and rotational relaxation of iodine in seeded supersonic beamsThe Journal of Physical Chemistry, 1979
- Metastable fragment production following electron impact on CO2Journal of Physics B: Atomic and Molecular Physics, 1976
- Laser fluorescence study of the equilibration of excited vibrational states of SF6 during SF6-rare gas collisionsThe Journal of Chemical Physics, 1973
- Vibrational Relaxation in Gas-Dynamic FlowsAnnual Review of Fluid Mechanics, 1970
- The transfer of vibrational energy between moleculesProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1964