Photophysics and diffractive imaging of controlled gas-phase molecules

The understanding of the temporal evolution of a molecular systems on the atomic level is typically described by the term molecular movie. Recording of a full time- resolved molecular movie requires a temporal resolution in the order of femtoseconds and a spatial resolution of picometers. The control of gas-phase molecules can be highly advantageous or simply necessary for the recording of such a movie. Here, “control“ refers to the spatial separation of different quantum states, conformers, or clusters, and the alignment or orientation of the molecular axes in space. We present two experiments which are utilizing the different types of control, i.e., spatial separation and alignment, as a preparation step for the recording of such a molecular movie.At first, the photophysics of spatially separated indole, and indole-water1 clusters, i.e., indole ‘solvated’ by a single water molecule, will be discussed. The spatial separation allowed to purify the indole-water1 clusters, which were otherwise hidden in the soup of different generated clusters, to study the influence of the hydrogen- bonded water on the photofragmentation of indole. Photofragmentation was induced by side specific 1s core hole ionization of the indole’s nitrogen or carbon atom. Emitted electrons and ionic fragments were recorded in coincidence, and the different fragmentation channels of the different species will be discussed.Strongly aligned molecules were used to image gas-phase molecules with atomic resolution via diffractive imaging, which is a promising tool to unravel ultrafast molecular dynamics [3,4], such as isomerization, folding, or photofragmentation. Here, 2,5-diiodothiophene molecules were laser-aligned in the so-called ‘intermediate regime’ between adiabatic and impulsive alignment [5]. The laser pulses had a pulse duration of 94 ps and were provided by a Ti:Sapphire laser system. The strongly aligned molecules were probed by (hard) x-ray radiation (9.5 keV) provided by the Linac Coherent Light Source (LCLS). The alignment procedure as well as the outcome of the experiment will be discussed.[1] Trippel, Chang, Stern, Mullins, Holmegaard, Küpper, Phys. Rev. A. 86, 033202 (2012) [2] Chang, Horke, Trippel, Küpper, Int. Rev. Phys. Chem. 34(4), 557-590 (2015)[3] Küpper et al. (53 authors), Phys. Rev. Lett. 122(8), 083002 (2014)[4] Barty, Küpper, Chapman, Ann. Rev. Phys. Chem. 64(1), 415-435 (2013)[5] Kierspel et al. (30 authors), J. Phys. B. 48(20), 204002 (2015