Rydberg fluorescence of NO trapped in rare gas matrices

Abstract

Fluorescence spectra from the Rydberg A 2Σ+ (v=0) level of NO trapped in Ne, Ar, Kr, and Xe matrices have been obtained for two different sites. The main site is characterized by broad A(0,v″) bands (FWHM≂80 meV), blue gas-to-matrix shifts of 70 to 300 meV, and by absorption–emission Stokes shifts of 300 meV in Xe to 800 meV in Ne matrices. The line shapes and Stokes shifts are treated within a configuration coordinate model by a moment analysis. A linear and quadratic coupling is invoked with relaxation energies ranging for the excited state from 160 meV in Xe to 540 meV in Ne and for the ground state from 150 meV in Xe to 280 meV in Ne and an increase of the cage radius of 3% in Xe to 15% in Ne. The ‘‘red’’ site fluorescence shows emission bands with matrix shifts of −140 meV in Xe to 80 meV in Ne and absorption–emission Stokes shifts of 210 meV in Xe to 830 meV in Ne. Red site ‘‘hot’’ A (v=1) fluorescence is also observed. Red sites are attributed to local disorder around the molecule in Ar, Kr, and Xe matrices and to hexagonal close packed (hcp) pockets within the face centered cubic (fcc) lattice in the case of Ne matrices.