Hannover 2010 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 15: Attosecond Physics I
A 15.8: Vortrag
Mittwoch, 10. März 2010, 18:15–18:30, F 107
High Harmonic Transient Grating Spectroscopy — •Markus Gühr1,2, Joseph P. Farrell1,2, Limor S. Spector1,2, Brian K. McFarland1,2, Mette Gaarde1,3, Kenneth Schafer1,3, and Philip H. Bucksbaum1,2 — 1Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, USA — 2Physics and Applied Physics, Stanford University, USA — 3Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
High harmonic generation (HHG) spectra contain valuable information about the electronic structure of the generation medium, information that has proven to be powerful for monitoring molecular and atomic ground states. All HHG experiments on excited atomic or molecular states suffer from a ground state harmonic background, thereby reducing excited state sensitivity. We use a transient grating (TG) scheme to overcome this problem and also obtain spectrally resolved high harmonics without the need for a spectrometer. We imprint a 400 nm excited state grating structure on the HHG medium by two counterpropagating 800 nm pulses. A strongly focused 800 nm probe pulse hits the grating under a shallow angle. The harmonics of order n are scattered into the Bragg angle θBragg=asin(1/n). We test the scheme with plasma gratings in argon gas and molecular alignment gratings in N2. The generated harmonics are scattered into their respective Bragg angle and we observe up to 6 spectrally resolved harmonics that show enhanced sensitivity to the atomic or molecular excitation.