Speaker
Description
I will show how laser pulses can align molecules in helium nanodroplets and how the ability to place molecules in advantageous spatial orientations allows structural determination of molecular complexes. The talk will focus on the following topics:
1) Alignment of molecules with pulses much shorter than the molecular rotational periods.
The experimental results show rotational dynamics that differs completely from that of isolated molecules [1]. Notably, pronounced oscillations in the time-dependent molecular alignment, with no counterpart in gas phase molecules, are observed. Angulon theory identifies the oscillations to originate from the unique rotational structure of molecules in He droplets [2].
2) Alignment induced by pulses that are turned-on (quasi) adiabatically.
It will be shown how the 0.4 K temperature of the molecules inside the droplets enables unprecedented high degrees of alignment, in either one or three dimensions. The method applies to large, complex molecules and the alignment can be made field-free by rapidly switching off the alignment pulse [3].
3) Femtosecond-laser-induced Coulomb explosion imaging of the structure of molecular dimers and trimers created inside He droplets.
Results for both small linear molecules, including CS2 [4] and OCS, and the larger molecule tetracene, are presented. Perspectives for time-resolved imaging of bimolecular reactions and interactions are discussed.
[1] B. Shepperson, A. A. Søndergaard, L. Christiansen, J. Kaczmarczyk, R. E. Zillich, M. Lemeshko, and H. Stapelfeldt, Phys. Rev. Lett. 118, 203203 (2017).
[2] I. N. Cherepanov, G. Bighin, L. Christiansen, A. V. Jørgensen, R. Schmidt, H. Stapelfeldt, and M. Lemeshko, in preparation (2019).
[3] A. S. Chatterley, C. Schouder, L. Christiansen, B. Shepperson, M. H. Rasmussen, Henrik Stapelfeldt, Nat. Comm. 10, 133 (2019).
[4] J. D. Pickering, B. Shepperson, B. A. K. Hubschmann, F. Thorning and H. Stapelfeldt, Phys. Rev. Lett. 120, 1121321 (2018).
