Radiationless decay of the 1,2,3 [sup 3][Pi][sub [ital g]] states of Al[sub 2]: A fully first principles treatment using adiabatic and rigorous diabatic states

Journal Article · Wed Feb 01 00:00:00 EST 1995 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468762· OSTI ID:6601688

Han, S; Hettema, H; Yarkony, D R ^[1]

---

1. Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)

The decay mechanisms of the metastable 2,3 [sup 3][Pi][sub [ital g]] states of Al[sub 2] are investigated. Both nonadiabatic radiationless decay to the dissociative 1 [sup 3][Pi][sub [ital g]] state and radiative decay to the ground [ital X] [sup 3][Pi][sub [ital u]] state are considered. The 1,2,3 [sup 3][Pi][sub [ital g]] states are described using state averaged multiconfiguration self consistent field/configuration interaction wave functions [[psi][sup [ital a]][sub [ital m]]([bold r],[ital Q])]. The derivative couplings [ital f][sup [ital a]][sub [ital mn]]([ital Q])[equivalent to][l angle][psi][sup [ital a]][sub [ital m]]([bold r], [ital Q])[vert bar]([ital d]/[ital dQ])[psi][sup [ital a]][sub [ital n]]([bold r],[ital Q])[r angle][sub [bold r]] are determined and used to construct a rigorous diabatic basis for this strongly interacting three state problem. The 2 [sup 3][Pi][sub [ital g]] state and somewhat surprisingly the 3 [sup 3][Pi][sub [ital g]] state are rapidly predissociated by the dissociative 1 [sup 3][Pi][sub [ital g]] state. The lifetimes for nonradiative decay of the vibrational levels of the 2 [sup 3][Pi][sub [ital g]] state are on the order of picoseconds while those of the 3 [sup 3][Pi][sub [ital g]] state are on the order of nanoseconds being reduced from the direct coupling (3 [sup 3][Pi][sub [ital g]][similar to]1 [sup 3][Pi][sub [ital g]]) rate of milliseconds by indirect coupling through the 2 [sup 3][Pi][sub [ital g]] state, (3 [sup 3][Pi][sub [ital g]][similar to]2 [sup 3][Pi][sub [ital g]][similar to]1 [sup 3][Pi][sub [ital g]]). Radiative decay is found to be on the order of 10[sup 2] and 30 ns for the 2 [sup 3][Pi][sub [ital g]] and 3 [sup 3][Pi][sub [ital g]] states, respectively, so that radiationless decay is principal decay mechanism. Significant variation in the lifetimes of the individual vibrational levels of the 2,3 [sup 3][Pi][sub [ital g]] states is expected.

• DOE Contract Number: FG02-91ER14189
• OSTI ID: 6601688
• Journal Information: Journal of Chemical Physics; (United States), Vol. 102:5; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ALUMINIUM
METASTABLE STATES
DIMERS
ADIABATIC APPROXIMATION
DIABATIC APPROXIMATION
GROUND STATES
LIFETIME
PREDISSOCIATION
RADIATIONLESS DECAY
RADIATIVE DECAY
VIBRATIONAL STATES
DE-EXCITATION
DECAY
DISSOCIATION
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
METALS
PARTICLE DECAY
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)