State-to-state studies of the collisional quenching of electronically excited Cd(/sup 1/P/sub 1/) atoms

Journal Article · Sun Mar 15 04:00:00 EST 1981 · J. Chem. Phys.; (United States)

OSTI ID:6524123

Breckenridge, W H; Malmin, O K

A comprehensive study of the quenching of electronically excited Cd (5s5p /sup 1/P/sub 1/) by a variety of simple molecules has been conducted using pulsed laser techniques. Except for He, Ar, and C/sub 2/F/sub 6/, deactivation occurs at essentially every encounter with all quenchers studied. The following process occurs with high efficiency with most of the quenching molecules studied, in striking violation of the Wigner spin rule and in spite of other available chemical or energy-transfer exit channels in many cases: Branching ratios for total Cd(5s5p/sup 3/P/sub J/) production were determined using an indirect method calibrated by earlier absolute measurements. Initial distributions of individual Cd(/sup 3/P/sub 2,1,0/) quantum states in process (1), determined by a pump-and-probe laser-induced fluorescence technique, show wide variations for different types of molecular quenchers. A qualitative model of bond-specific interactions of Cd(/sup 1/P/sub 1/) with quenching molecules has been developed which successfully rationalizes all the experimental results. For several of the molecules, and electronically statistical (5:3:1) distribution of Cd(/sup 3/P/sub 2,1,0/) is observed and attributed to a preponderance of bond sites at which there is a net attractive interaction of Cd(/sup 1/P/sub 1/), caused either by intersection of ionic surfaces (N/sub 2/,CO) or by chemical bonding (alkyl C--H bonds), so that crossings occur with equal probability to all repulsive states correlating with Cd(/sup 3/P/sub 2,1,0/). Cases for which the Cd(/sup 3/P/sub 2,1,0/) distribution is skewed away from statistical towards Cd(/sup 3/P/sub 2/) (Ar, CH/sub 4/, C/sub 2/H/sub 6/, C(CH/sub 3/)/sub 4/, C/sub 3/H/sub 8/) result from a less attractive potential with Cd(/sup 1/P/sub 1/) (due to stronger C--H bonds and/or weaker dispersion forces) and preferential crossings with the most repulsive ''..sigma..''-like states, which correlate with Cd(/sup 3/P/sub 2,1,0/).

• Research Organization: Department of Chemistry, University of Utah, Salt Lake City, Utah 84112
• OSTI ID: 6524123
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 74:6; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALKANES
ALKENES
ARGON
ATOM COLLISIONS
ATOM-ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CADMIUM
CHALCOGENIDES
COLLISIONS
DE-EXCITATION
ELECTROMAGNETIC RADIATION
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
ETHANE
FLUIDS
GASES
HELIUM
HYDROCARBONS
LASER RADIATION
METALS
METHANE
MOLECULE COLLISIONS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
RARE GASES