Rydberg states of NO trapped in rare gas matrices

Abstract

Several new progressions consisting of broadbands have been observed in the absorption spectra of NO trapped in rare gas matrices. They are identified as the blue shifted transitions to the n=3 (A 2Σ+,C 2Π,D 2Σ+) and n=4 (E 2Σ+,K 2Π,M 2Σ+) Rydberg states of NO in Ne matrices and to the n=3 Rydberg states in Ar, Kr, and Xe matrices. Linewidths (50 to 180 meV) and matrix shifts (0.3 to 1.2 eV) decrease from neon to xenon matrices. For each matrix, the shifts decrease according to the symmetry of the excited state orbital, in the sequence sσ–pσ–pπ. An attempt to apply the quantum defect formula with values, for the Rydberg constant and the ionization potential of the matrix isolated molecule taken from literature, fails to describe the vertical transition energies of n=3 and n=4 states in neon matrices. On the other hand, using the adiabatic energies of 3sσ and 4sσ states to generate a series shows that the vertical transitions of n≥5 states lie in the ionization continuum. This could explain the nonobservation of n>4 states in Ne matrices. In the heavier matrices, this model predicts n=4 states but their existence is not borne out by experiment. The Wannier model also fails to describe these transitions.