Femtosecond transition state spectroscopy of solids: electronic ‘bubble’ formation in solid hydrogen

We report the femtosecond nuclear dynamics of an electronic ‘bubble’ in solid H2. The bubble formation results from the impulsive excitation of the lowest Rydberg state A2 Σ+ (3sσ) of the NO impurity by a UV femtosecond pulse. The evolution of the bubble was followed in real-time by means of a probe pulse which maps the transient configurations by inducing transitions to higher-lying Rydberg states. It is found that the bubble is formed coherently by the collective displacement of the matrix species, without recurrences (coherent or incoherent) of the cage motion. The bubble reaches its final configuration in ∼ 1.5 ps.