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MO: Molekülphysik
MO 6: Dissociation and other Collision Processes
MO 6.1: Group Report
Tuesday, April 3, 2001, 15:45–16:15, H1058
Critical internuclear distances in laser-induced Coulomb explosion of H2+ and D2+ — •Domagoj Pavičić, Hartmut Figger, Karsten Sändig, and Theodor W. Hänsch — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching
In distinction from former similar experiments, H2+ and D2+ molecular ions were generated in a DC discharge and formed in a mass selected strongly collimated beam. After previously studying the dissociation where H atoms and protons are formed by one and more photon absorption, now the photoionisation by absorption of many photons is studied.
In the experiment the molecular ions were exposed to 80-fs laser light of 1· 1014 to 5· 1014 W/cm2 in peak intensity. The charged fragments resulting from Coulomb repulsion were projected on a two-dimensional multichannel plate detector. Due to the high momentum resolution and signal-to-noise ratio, the peaks in the Coulomb explosion energy spectrum have been clearly distinguished for the first time. Their corresponding values of the critical internuclear separations of approximately 6, 8 and 10 a.u., at which ionisation occurs, are in good agreement with the theoretical calculations for H2+[1]. The measurements on D2+ have yielded the similar values. At higher intensities, the peak structure vanishes and the energy spectrum takes a plateau like shape. The angular distribution of Coulomb explosion fragments is sharply peaked in the laser polarisation direction with the FWHM of approximately 30∘.
[1] A. D. Bandrauk and H. Z. Lu, Phys. Rev. A 62, 053406 (2000)