TY - JOUR
T1 - Infrared double resonance in sulfur hexafluoride
AU - Steinfeld, J. I.
AU - Burak, I.
AU - Sutton, D. G.
AU - Nowak, A. V.
PY - 1970
Y1 - 1970
N2 - The relaxation of sulfur hexafluoride has been monitored by observation of infrared absorption intensities following passage of an infrared laser pulse through the gas. The laser pulse saturates a small number of rotational lines in the v3←-0 transition of SF6 at 944 cm-1, producing a transient "hole" in the absorption spectrum at that frequency. This hole is filled in very rapidly by rotational relaxation processes. The specific vibrational excitation is, at essentially the same time, transformed into a vibrational temperature in excess of the gas's translational temperature, by means of very efficient vibration ↔ vibration energy transfer collisions. The energy released in this step also heats the gas translationally by the order of 25°K. The vibrational temperature then relaxes to the translational temperature by a binary collision process, with Pτ- (122±8) μsec-torr in pure SF6. The rate-controlling step is concluded to be the vibration→translation relaxation of the v6 level at 363 cm-1. The mean efficiency per collision of this step has been measured for He,Ne,Ar, Kr, C2H6, (CH3) 2O,CH4,CH3Br, CHF2Cl, H 2O, H2, N2,and Cl2,inaddition to SF6 itself.Atransient absorption spectrum arising from the vibrationally hot SF6 is also given. The slowest relaxation observed in the system is the bulk cooling of the translational temperature of the gas, which occurs in the order of milliseconds under typical experimental conditions. The dominant mechanism for this relaxation appears to be cooling by thermal conduction.
AB - The relaxation of sulfur hexafluoride has been monitored by observation of infrared absorption intensities following passage of an infrared laser pulse through the gas. The laser pulse saturates a small number of rotational lines in the v3←-0 transition of SF6 at 944 cm-1, producing a transient "hole" in the absorption spectrum at that frequency. This hole is filled in very rapidly by rotational relaxation processes. The specific vibrational excitation is, at essentially the same time, transformed into a vibrational temperature in excess of the gas's translational temperature, by means of very efficient vibration ↔ vibration energy transfer collisions. The energy released in this step also heats the gas translationally by the order of 25°K. The vibrational temperature then relaxes to the translational temperature by a binary collision process, with Pτ- (122±8) μsec-torr in pure SF6. The rate-controlling step is concluded to be the vibration→translation relaxation of the v6 level at 363 cm-1. The mean efficiency per collision of this step has been measured for He,Ne,Ar, Kr, C2H6, (CH3) 2O,CH4,CH3Br, CHF2Cl, H 2O, H2, N2,and Cl2,inaddition to SF6 itself.Atransient absorption spectrum arising from the vibrationally hot SF6 is also given. The slowest relaxation observed in the system is the bulk cooling of the translational temperature of the gas, which occurs in the order of milliseconds under typical experimental conditions. The dominant mechanism for this relaxation appears to be cooling by thermal conduction.
UR - http://www.scopus.com/inward/record.url?scp=51149217356&partnerID=8YFLogxK
U2 - 10.1063/1.1672793
DO - 10.1063/1.1672793
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:51149217356
SN - 0021-9606
VL - 52
SP - 5434
EP - 5441
JO - The Journal of Chemical Physics
JF - The Journal of Chemical Physics
IS - 10
ER -