Crossed beam photodissociation imaging of HeH+ with vacuum ultraviolet free-electron laser pulses

Abstract

Molecular photofragmentation has been studied by event imaging on HeH+ ions at 32 nm (38.7 eV) in a fast ion beam crossed with the free-electron laser in Hamburg (FLASH), analyzing neutral He product directions and energies. Fragmentation into He(1snl,n≥2)+H+ was observed to yield significant photodissociation at 32 nm with an absolute cross section of (1.4±0.7)×10-18cm2, releasing energies of 10-20 eV. A clear dominance of photodissociation perpendicular to the laser polarization was found in contrast to the excitation paths so far emphasized in theoretical studies. © 2007 The American Physical Society.