Two-dimensional electron angular distributions from aligned molecules

Vinod Kumarappan
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

Lotte Holmegaard, Christian Martiny, Christian Madsen, Thomas Kjeldsen, Simon Viftrup, Lars Madsen, Henrik Stapelfeldt
Aarhus University, Denmark

We report the measurement of 2D electron angular distributions from multiphoton single ionization of aligned CS2 molecules. CS2 molecules were cooled in a supersonic expansion and aligned non-adiabatically using a Ti:Sapphire laser pulse (800 nm, 0.5 ps, 2.9 x 1012 W/cm2) without significant ionization, and a time-delayed second pulse (25 fs, 7.7 x 1013 W/cm2) was used to singly ionize the molecules at best alignment at the first half-revival. 2D electron momentum spectra were measured using velocity map imaging as a function of angle between the alignment axis and the polarization vector of the ionizing pulse. The angular distribution was found to depend significantly on this angle. Calculations using molecular strong-field approximation were found to account for some, but not all, of the features seen in the experiment. The measurement of molecular-frame photoelectron angular distributions provides new challenges and more stringent tests for theoretical description of molecular ionization by intense lasers.

This work was supported by the Carlsberg Foundation, the Lundbeck Foundation and the Danish National Research Council.

Presented at DAMOP, May 2008, in State College, PA.


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