A two-laser pulse-and-probe technique is used to study photofragmentation of Br2 and IBr over the wavelength range 450-530 nm. The metastable Br(2P1/2-2P3/2) transition is probed by time-resolved laser gain vs absorption spectroscopy using a tunable color center laser. This new approach to the measurement of quantum yields provides highly accurate absolute values for Br*(2P1/2) production. The peak quantum yield for Br2 photodissociation is φ = 87% at λ = 500 nm. The difference between the spectral variation of φ and the total absorption spectrum characterizes the A state of bromine, which contributes ≲ 14% to the absorption spectrum at λ = 510 nm. The peak in the Br* yield from photofragmentation of IBr is φ ∼ 73% at λ = 500 nm. The present absolute IBr data together with the previous molecular beam studies suggest a reassessment of the contributions of the continuum states in IBr. The laser gain vs absorption method for obtaining quantum yields is readily generalized to other atoms and molecules.
|Original language||English (US)|
|Number of pages||11|
|Journal||The Journal of Chemical Physics|
|State||Published - Jan 1 1985|
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry