Time-resolved photoelectron spectroscopy of 4-(dimethylamino)benzethyne – an experimental and computational study

Abstract

We investigated the excited-state dynamics of 4-(dimethylamino)benzethyne (DMABE) in a combined theoretical and experimental study using surface-hopping simulations and time-resolved ionisation experiments. The simulations predict a decay of the initially...

Ab Initio Simulation of the Ultrafast Circular Dichroism Spectrum of Provitamin D Ring-Opening

“…On the microsecond to second time-scale, this is a standard tool to study conformational changes in biomolecules, such as proteins and nucleic acids. , However, due to noise caused by density fluctuations of the achiral background, the overall sensitivity of CD is rather small, which makes its application for ultrafast pump–probe spectroscopy challenging. , Thanks to advances in the experimental setup, large progress has been made in recent years, leading to pump–probe TRCD spectroscopy with time-resolutions of 1 ps and below. − While the first ultrafast TRCD measurements with subpicosecond resolution were restricted to fixed wavelengths, recent advances in increasing the sensitivity also allow the broadband measurement of the TRCD. , As common in pump–probe spectroscopy, the TRCD signal can be fitted to decay functions, yielding overall relaxation rates. , However, oftentimes the TRCD contains an oscillatory fine structure, which is usually neglected in the analysis but may potentially give more information about the structural dynamics. To obtain a relationship between the oscillatory structure of the TRCD, we apply nonadiabatic excited state molecular dynamics simulations, − which have been shown to provide structural information on the photodynamics in a variety of organic systems , and are therefore well-suited to complement pump–probe experiments. − Here, we apply time-dependent density functional theory surface hopping (TDDFT-SH) molecular dynamics simulations to model the TRCD along the photoinduced ring-opening reaction of provitamin D in the gas phase. This reaction constitutes the initial step in natural vitamin D photosynthesis.…”