Ultrafast structural dynamics in electronically excited solid neon. I. Real-time probing of the electronic bubble formation

The dynamics of electron "bubble" formation upon excitation of the A(3ssigma) Rydberg orbital of NO in solid Ne was investigated by means of conventional spectroscopy and femtosecond pump-probe spectroscopy. The femtosecond pump pulse initiates the formation of a bubble by the expansion of the Ne atoms surrounding the NO impurity, generating a wave packet of intermolecular NO-matrix modes. The dynamics exhibits a first peak due to the sampling of the initial expansion of the bubble followed by at least one oscillation of the bubble boundaries, which occurs similar to1.3 ps after the start of the dynamics and is significantly broader than the first peak. The whole process of bubble formation and stabilization is over by 2-3 ps in which 0.54 eV are released into the lattice. This suggests a sudden, probably shock-wave-like, emission of energy into the lattice. We directly extract in a first approximation the time dependence of the bubble radius from the pump-probe transients. This trajectory is used to simulate the experimental data with good agreement. Paradoxically, even though solid Ne is a lighter solid, the overall dynamics (expansion and recurrence) are slower than for the heavier argon solid.