They carry out HHG in Methane and Xeon using two colours and show a suppression of the HHG signal in Methane in the presence of a .weak. 1500-1900 field from an OPA which is resonant with a vibration transition in Methane. This has quite a lot of cross over with work that has been done or is being carried out with the Red Dragon lab.
We experimentally investigate the high harmonic generation (HHG) from
CH4 molecules and Xe atoms in a two-color field (using the 800nm laser
and the tunable laser with the longer wavelength from 1500nm to 1900nm),
and observe that the longer wavelength component can destructively
suppress the HHG from CH4 molecules. By controlling the time delay
between the two color laser pulses or tuning the laser intensity of the
longer wavelength component, the suppressions of the HHG from CH4
molecules and the enhancements of the HHG from Xe atoms at the same
laser condition are observed. The results indicate that the longer
wavelength component around the molecular infrared absorption can
suppress the molecular HHG process.
PPT slides to follow...