Measurement of the lifetime of metastable triatomic hydrogen

Journal Article · Thu Nov 01 04:00:00 EST 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.458999· OSTI ID:6230046

Bordas, C; Cosby, P C; Helm, H ^[1]

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1. Molecular Physics Laboratory, SRI International, Menlo Park, California 94025 (USA)

We measured the survival probability of the metastable ({ital N}=0, {ital K}=0) level of the 2{ital p}{sup 2}{ital A}{sup {double prime}}{sub 2} of H{sub 3} as a function of time elapsed from formation of the molecule by probing its population with photoionization. We find lifetimes {tau}=640{sup +300}{sub {minus}100} ns for the ground vibrational state and {tau}=740{sup +300}{sub {minus}100} ns for the symmetric stretch-excited level. Equally short lifetimes are obtained from an analysis of the photoinduced bleaching of the spontaneous dissociation signal of metastable H{sub 3}. These lifetimes are about 2 orders of magnitude shorter than those expected on the basis of the allowed radiative transition 2{ital p}{sup 2}{ital A}{double prime}{sub 2}{r arrow}2{ital s}{sup 2}{ital A}{sup {prime}}{sub 2}. We attribute the faster decay channel to weakly allowed radiative transitions between the metastable state and the degenerate mode-excited repulsive ground state of H{sub 3}, as well as to predissociation of the metastable levels by the repulsive ground state of H{sub 3} induced by spin--orbit coupling.

• OSTI ID: 6230046
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 93:9; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
COUPLING
DISSOCIATION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
HYDROGEN
INTERMEDIATE COUPLING
IONIZATION
L-S COUPLING
LIFETIME
METASTABLE STATES
MOLECULES
NONMETALS
PHOTOIONIZATION
POLYATOMIC MOLECULES
PREDISSOCIATION