Wavelength-dependent photodissociation of a prototypical chiral moleculeiodomethylbutane
Valerija Music
University of Kassel, Germany
: Res J Opt Photonics
Abstract
Photodissociation, which evolves to a large extent on femtosecond timescales, plays an important role in the study of various biological, chemical, and physical processes. The investigation of photodissociation on atomic scales provides valuable insight into different dynamics and pathways of molecular fragmentation and is only directly accessible via pulsed light sources with durations in the order of the dynamics of interest or better. Favorable light sources are free-electron lasers (FELs)1, which produce ultrashort and ultrabright pulses in the XUV and X-ray regime. Due to their short wavelength, they possess the ability of site- and element-selective inner-shell photoionization. Experiments can be performed with very high temporal and spatial resolution. This is a big advantage because localized states, as core-holes, can provide a very distinct view of the evolving system. Therefore, optical laser (OL)-pump and FEL-probe schemes are nowadays widely used. The OL triggers individual dissociation pathways, which are then probed via time-delayed FEL pulses. Via the variation of the time delay between the pump and probe pulses, time-resolved studies can be performed. We present a study, where highly intense XUV pulses of the Free-Electron-LASer in Hamburg (FLASH)2 were used to probe the OL-induced fragmentation of the prototypical chiral molecule Iodomethylbutane (C5H11I) in a pump-probe scheme using 267 nm and 800 nm pulses of a Ti:Sapphire3 laser. Ion velocity-map images4 and time-of-flight spectra5 were obtained utilizing a double-sided Velocity-Map-Imaging spectrometer6 . For probing the different fragmentation channels of the iodine 4d edge, two different photon energies, i.e. 63 eV (neutral iodine)7 and 75 eV (singly charged iodine)7,8, were used. OL-pump XUV-probe scans reveal that the molecule dissociates significantly slower with an 800 nm pump than with a 267 nm pump. The results show substantial wavelength and intensity dependence for the OL-induced dissociation dynamics and provide an extended basis for future time-resolved studies.
Biography
Valerija Music is a Ph.D. student in AMO physics at the University of Kassel in Germany. She conducts her research at FEL facilities and is therefore permanently located in Hamburg at DESY and European XFEL. The main scope of her work is the investigation of ultrafast dynamics in chiral systems via photoelectron circular dichroism9,10,11,12,13 as a tool for chiral recognition. She has expertise in building and running VMI spectrometers for performing experiments at XUV and soft X-ray beamlines of large-scale facilities such as FELs and synchrotrons. She is part of several international research collaborations and experimental FEL campaigns.
