Tunneling and decay dynamics of H̄ 1Σg+ outer well states in hydrogen

Abstract

We present an experimental study of the decay dynamics of rovibrational states confined in the outer minimum of the HH̄ 1Σg+ potential of the hydrogen molecule. Specific (v,J) quantum states are populated using a two-step excitation process involving a pulsed extreme ultraviolet laser source. Decay products are selectively probed with additional laser pulses, using the timing of these pulses to determine lifetimes. The competition between dissociation and ionization, occurring at short internuclear distance after tunneling through the potential barrier, is addressed. Observed lifetimes and decay channels of H̄ levels are consistent with a semiclassical description of tunneling of the nuclear motion through the potential barrier towards small internuclear distance. For the HD isotopomer breaking of the g−u symmetry is found to strongly affect the decay dynamics.