Structural dynamics in quantum solids. I. Steady-state spectroscopy of the electronic bubble in solid hydrogens

The structural changes due to formation of electronic bubbles in solid D2 are investigated by means of fluorescence, fluorescence-excitation, and fluorescence-depletion spectroscopy of the lowest Rydberg state, A Σ+2(3sσ), of the NO impurity. The A←X band is strongly blueshifted (∼0.7 eV) with respect to the gas phase and shows a very broad (full width at half maximum ∼2000 cm−1) and asymmetric profile. The shift results from the strong repulsion due to the overlap of the extended Rydberg orbital with the matrix species, while the width and asymmetry are governed by quantum effects on the ground-state intermolecular wave function. Fluorescence occurs with large absorption-emission Stokes shifts, bringing the A-state emission energy to its gas-phase value, which indicates a very loose cavity around the excited molecule. A line-shape analysis of the A-X absorption and emission bands allows us to extract one-dimensional intermolecular NO-matrix potentials of both involved states. We estimate the bubble radius to ∼5 Å, in good agreement with values from the literature for the bubble radius of the solvated electron. Fluorescence-depletion spectra of the A state are also presented along with the ground-state transitions to the higher C Π2Π(3pπ) and D Σ+2(3pσ) states. They are used to generate intermolecular potentials for the C and D states, which are essential ingredients for ultrafast pump–probe experiments of the bubble dynamics. The results obtained for D2 matrices are compared with those previously published for H2 matrices.