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 04:00:00 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), Journal Name: J. Chem. Phys.; (United States) Vol. 73:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

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