Laser induced alignment of molecules in Helium droplets
Thursday, 05 Sep. 2013, 11:00 - 12:00
Presenter: Prof. Henrik Stapelfeldt
Host: Prof. Markus Arndt
Where: Ernst Mach Hörsaal, 2nd floor Boltzmanngasse 5, 1090 Vienna
Laser induced alignment, the method to confine the principal axes of molecules along axes fixed in the laboratory frame, is now used in a range of applications in physics and chemistry. With a few exceptions all studies have focused on isolated molecules in the gas phase.
In this talk I present experimental studies of laser induced alignment of molecules embedded helium nanodroplets. Alignment is conducted in both the adiabatic and the nonadiabtic regime where the alignment pulse is much longer or shorter, respectively, than the rotational period of the molecules.
In the nonadiabatic limit, induced by a few-hundred femtosecond long laser pulse, I show that methyliodide molecules reach an alignment maximum 20 ps after the alignment pulse and gradually loose the alignment completely in another 60 ps . This dynamics is completely different from that of isolated methyliodide molecules where alignment occurs in regularly spaced (by 33.3 ps), narrow time windows, termed revivals. Adiabatic alignment, induced by a 10 ns laser pulse, resembles, on the other hand, the gas phase behavior .
 D. Pentlehner et al., Phys. Rev. Lett. 110, 093002 (2013)  D. Pentlehner et al., Phys. Rev. A 87, 063401 (2013)