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MO: Molekülphysik

MO 20: Femtosekundenspektroskopie VII: Intensive Laserfelder, Erzeugung hoher Harmonischer (gemeinsam mit FV Q)

MO 20.2: Vortrag

Freitag, 8. März 2002, 11:15–11:30, HS 15/E07

Dissociation and Coulomb explosion of H₂ ⁺, D₂ ⁺ and HD ⁺ molecular ions in intense laser fields — •Domagoj Pavičić, Hartmut Figger, and Theodor W. Hänsch — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

At intensities >10¹⁴ W/cm² dissociation of H₂ ⁺ and its isotopomers is accompanied by ionisation followed by Coulomb repulsion of nuclei. We studied both fragmentation mechanisms using fast beams of the molecular ions generated in DC discharges. This eliminated the influence of the first ionisation step in experiments done on the neutral molecules. The ions in the highly collimated beams were subjected to intensities up to 10¹⁵ W/cm² of 80 fs pulses from a 1 kHz Ti:Sapphire laser system. The neutral and proton fragments from both mechanisms were imaged on a 2-dimensional multichannel plate detector. This gives direct information about both the energy and angular distribution of fragments. The original 3-dimensional momentum distribution was obtained by applying the inverse Abel transformation. Due to the high energy resolution, the fragments from different vibrational levels of H₂ ⁺ were resolved. In addition to previously reported 1-photon peaks in the dissociation channel, we recently observed fragments coming from vibrational levels v=1-3 via 3-photon bond-softening. The Coulomb explosion energy spectrum showed structure that partly agrees with results from the charge-resonant enhanced ionisation theory (CREI), in particular concerning the No-dqcriticalNo-dq internuclear separations. The angular distribution in the Coulomb explosion channel was much narrower than in the dissociation channel.