Ultrafast Photo‐ion Probing of the Ring‐Opening Process in Trans‐Stilbene Oxide

Abstract

The ultrafast photo‐induced ring opening of the oxirane derivative trans‐stilbene oxide has been studied through the use of ultrafast UV/UV pump‐probe spectroscopy by using photo‐ion detection. Single‐ and multiphoton probe paths and final states were identified through comparisons between UV power studies and synchrotron‐based vacuum ultraviolet (VUV) single‐photon ionization studies. Three major time‐dependent features of the parent ion (sub‐450 fs decay, (1.5±0.2) ps, and >100 ps) were observed. These decays are discussed in conjunction with the primary ring‐opening mechanism of stilbene oxide, which occurs through C−C dissociation in the oxirane ring. The appearance of fragments relating to the masses of dehydrogenated diphenylmethane (167 amu) and dehydrogenated methylbenzene (90 amu) were also investigated. The appearance of the 167 amu fragment could suggest an alternative ultrafast ring‐opening pathway via the dissociation of one of the C−O bonds within the oxirane ring.

Non-Adiabatic Electronic and Vibrational Ring-Opening Dynamics resolved with Attosecond Core-Level Spectroscopy

“…Nevertheless, a tremendous challenge for existing methods is still the combined requirement for ultrafast time resolution [26][27][28] , the capability to disentangle time-overlapping electronic and nuclear dynamics 29 , and to follow radiation-less decay across transient and optical dark states 30 .…”

“…Prominent examples are the retinal isomerization 5 of the vision process and the photo-stability of DNA bases 6 . Due to the importance of valence electron dynamics, many methods were developed; e.g., ultrafast two-dimensional spectroscopy [7][8][9][10][11] , attosecond transient absorption [12][13][14] , time-resolved photoelectron spectroscopy 15-17 , x-ray spectroscopy 18,19 and high harmonic spectroscopy [20][21][22][23][24][25] .Nevertheless, a tremendous challenge for existing methods is still the combined requirement for ultrafast time resolution [26][27][28] , the capability to disentangle time-overlapping electronic and nuclear dynamics 29 , and to follow radiation-less decay across transient and optical dark states 30 .Here, we meet these combined challenges with attosecond core-level spectroscopy, which reveals the energy pathways and real-time conical intersection dynamics in photo-excited neutral furan and its vibrational dynamics on its native ultrafast time scale. The element and orbital selectivity of core-level spectroscopy, combined with attosecond temporal resolution, reveals the heterocyclic system's electronic and nuclear evolution predominantly into its ring-opening product.…”

Attosecond Core-Level Absorption Spectroscopy Reveals the Electronic and Nuclear Dynamics of Molecular Ring-Opening

“…CIs govern many vital processes, for instance, the retinal isomerization 6 of the vision process and the photo-stability of DNA bases 7 . The experimental challenge 6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] is the simultaneous tracing of the electronic and nuclear motion on the intrinsic ultrafast timescale [25][26][27] and following the system's radiation-less decay across transient and, often, optical dark states 28 .…”