Simultaneous measurement of rotational and translational relaxation by sub-Doppler optical--optical double resonance spectroscopy: BaO(A /sup 1/. sigma. /sup +/)--Ar and BaO(A/sup 1/. sigma. /sup +/)--CO/sub 2/

Journal Article · Tue Jul 15 00:00:00 EDT 1980 · J. Chem. Phys.; (United States)

OSTI ID:5328221

Gottscho, R A; Field, R W; Bacis, R; Silvers, S J

Sub-Doppler optical-optical double resonance spectroscopy is used to correlate BaO(A/sup 1/..sigma../sup +/) rotational and translational relaxation induced by collisions with Ar or CO/sub 2/ in a 0.3--2 Torr Ba+CO/sub 2/+Ar flame. A selected rovibronic BaO A /sup 1/..sigma../sup +/reverse arrowX /sup 1/..sigma../sup +/ transition is pumped by the first of two frequency stabilized, 1 MHz bandwidth, cw dye lasers. Collision-induced level-to-level processes in the A /sup 1/..sigma../sup +/ state are monitored with the second laser by excitation of C /sup 1/..sigma../sup +/reverse arrowA/sup 1/..sigma../sup +/ probe transitions and detection of C /sup 1/..sigma../sup +/..-->..X /sup 1/..sigma../sup +/ ultraviolet fluorescence. The dependence of J-changing collision rates on the initial A /sup 1/..sigma../sup +/ (v=1) rotational level, J/sub o/, is monitored by independent preparation of J/sub o/=0 and J/sub o/=15. For Ar, vertical-bar..delta..Jvertical-bar=1--20 collision rates are found to be independent of J/sub o/ and well represented by the power law, where ..delta..E/sub r/ is the change in BaO (A /sup 1/..sigma../sup +/) rotational energy in cm/sup -1/; epsilon=..delta..E/sub r/ for J/sub o/J. For BaOapprox.CO/sub 2/ collisions a single power law is inadequate to represent J/sub o/=0 and J/sub o/=15 data: Total BaO--Ar J-changing collision cross sections are: 60 +- 15 A/sup 2/ for J/sub o/=15 and 40 +- 10 A/sup 2/ for J/sub o/=0. For BaO--CO/sub 2/, total J-changing collision cross sections are: 230 +- 40 A/sup 2/ for J/sub o/=15 and 50 +- 20 A/sup 2/ for J/sub o/=0. ..delta..Jnot = 0 OODR line shapes, broadened by velocity changing collisions, sample the center of mass (cm) scattering angle (psi) distribution. For ..delta..J= +- 1 transitions, the cm scattering angle distribution is characterized by =0.81 +- 0.05 or =36/sup 0/ +- 5/sup 0/ for BaO--Ar and =0.989 +- 0.01 or =8.5/sup 0/ +- /sup 3//sub 6degree/ for BaOapprox.CO/sub 2/ collisions.

• Research Organization: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
• OSTI ID: 5328221
• Journal Information: J. Chem. Phys.; (United States), Vol. 73:2
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ARGON
ATOM-MOLECULE COLLISIONS
RELAXATION
BARIUM OXIDES
MOLECULE-MOLECULE COLLISIONS
CARBON DIOXIDE
ANGULAR MOMENTUM
CROSS SECTIONS
DOUBLE RESONANCE METHODS
ENERGY-LEVEL TRANSITIONS
ROTATIONAL STATES
SPECTROSCOPY
ALKALINE EARTH METAL COMPOUNDS
ATOM COLLISIONS
BARIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
COLLISIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
MOLECULE COLLISIONS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena