MATRIX-ISOLATED OXYGEN - LINE-SHAPES AND TRANSITION-PROBABILITIES OF THE B(1)SIGMA(-]X(3)SIGMA(-)(G), B(1)SIGMA(+)(G)-]A(1)DELTA(G) AND A(1)DELTA(G)-]X(3)DELTA(-)(G) TRANSITIONS()(G))

The b(1) Sigma(g)(+) <-> X(3) Sigma(g)(-), b(1) Sigma(g)(+) --> a(1) D elta(g) and a(1) Delta(g) --> X(3) Sigma(g)(-) transitions of molecula r oxygen isolated in Xe, Kr, Ar (2 sites) and Ne matrices have been st udied in excitation and emission. The radiative lifetimes of the isola ted monomers in these matrices are 9.5 + 0.3, 14.5 +/- 0.5, 24.5 +/- 1 and 46 +/-1 ms in the b state, and 11.5 +/- 0.5, 34 +/- 1, 68 +/- 2 a nd 146 +/- 3 s in the a state, The vibrational relaxation rates of the a, upsilon(1) = 1, level amount to 0.21, 0.18, 0.15 and greater than or equal to 0.14 s(-1). Dimers or otherwise perturbed oxygen molecules with shorter lifetimes have also been characterized. Relative intensi ty measurements of the involved electronic transitions show that the b -->, a and a --> X radiative transition probabilities are enhanced up to four orders of magnitude due to a phonon-induced transition dipole momenS giving rise to intense phonon sidebands with similar local mod e structure in both transitions. While the enhancement of the a --> X transition is probability attributed to intensity borrowing from the b --> a transition, the b --> X transition is only mildly affected by t he matrix. The ratio A(b-->): A(a-->x) of the Einstein coefficients fo r spontaneous emission in matrices compares well with the reported rat io for O-2 in CCl4 solution, supporting the intensity borrowing mechan ism. (C) 1997 Elsevier Science B.V.