H2 formation via non-Born-Oppenheimer hydrogen migration in photoionized ethane

Abstract

Neutral H2 formation via intramolecular hydrogen migration in hydrocarbon molecules plays a vital role in many chemical and biological processes. Here, employing cold target recoil ion momentum spectroscopy (COLTRIMS) and pump-probe technique, we find that the non-adiabatic coupling between the ground and excited ionic states of ethane through conical intersection leads to a significantly high yield of neutral H2 fragment. Based on the analysis of fingerprints that are sensitive to orbital symmetry and electronic state energies in the photoelectron momentum distributions, we tag the initial electronic population of both the ground and excited ionic states and determine the branching ratios of H2 formation channel from those two states. Incorporating theoretical simulation, we established the timescale of the H2 formation to be ~1300 fs. We provide a comprehensive characterization of H2 formation in ionic states of ethane mediated by conical intersection and reveals the significance of non-adiabatic coupling dynamics in the intramolecular hydrogen migration.

Direct Observation on H-Elimination Enhancement from C2H4 through Non-Adiabatic Process by Femtosecond Laser Induced Coulomb Explosion

“…This starting timescale of rising is also consistent with the results of previous studies (∼ 1000 fs). [40] In Fig. 5(b), we cannot observe a significant rise curve in ion counts for channel (3), which is also reflected in Fig.…”

“…These findings underscore the pivotal influence of non-adiabatic coupling dynamics on intramolecular hydrogen transfer mechanisms. [40] Our current research delves into the femtosecond dissociation dynamics of C2H4 cations, utilizing time-resolved Coulomb explosion imaging to capture the sequence of dissociation events triggered by strong-field ionization. Through the application of a delayed, intense laser pulse, we investigate varied dissociation routes of C2H4.…”

Structure and Ultrafast X-ray Diffraction of the Hydrated Metaphosphate

“…The integration range of r is separated into two parts: r < 1.8 Å and r > 1.8 Å. The time-resolved frequency analysis of the detrended autocorrelation function is performed using the continuous wavelet transformation (CWT) method, which has been widely used for vibrational analyses of MD. ,− As shown in Figure e, the peak intensity around ∼500 cm –1 corresponds to the P–O infrared excited vibrational modes. The decrease of intensity reflects the decay of the oscillation amplitude of the ΔPDF signal because the vibrational energy of P–O stretching is transferred from the solute to the solvent molecules.…”

“…Determining the reaction mechanisms and probing the structural dynamics of solvated molecules, such as enzymes and nucleic acids, are among the fundamental topics in chemical and biological science. Ultrafast X-ray and electron diffraction imaging methods have been widely used to resolve the structural and electronic dynamics in numerous studies for gas-phase molecules, − liquid solution, − and solids. − The advent of X-ray free-electron lasers (XFELs) has equipped the ultrafast X-ray diffraction imaging technique with Angstrom and femtosecond spatiotemporal resolution, enabling the direct observation of atomic motion and making “molecular movies”. − Besides ultrafast diffraction imaging, spectroscopic imaging methods are also widely used to study ultrafast structural dynamics in the liquid phase, such as proton transfer, isomerization, and charge transfer processes. − …”

Probing Conical Intersection in the Multipathway Isomerization of CH3Cl Using Coulomb Explosion

“…Hydrogen migration is a ubiquitous phenomenon in fuel cells, − proteomics, and biological chemistry − and has been studied in strong field laser-induced dissociation and ionization of simple hydrocarbons , and biomolecules. ,,, For these systems, multipathway reactions are prevalent, for example, photoionization of H 3 2+ , photoelectron migration in the In 2 O 3 /AgBr/Bi 2 WO 6 photocatalyst, formation of DNA secondary structures, and a conformational change in the alanine dipeptide . In the case of hydrogen migration, the fast and large-amplitude motion of light hydrogen atoms can induce strong non-adiabatic coupling of electronic states. − The non-adiabatic effects become significant at specific nuclear configurations called the conical intersections (CIs), where two or more potential energy surfaces (PES) are energetically degenerate, , and nonradiative transitions between electronic states can occur. − The non-adiabatic transitions near CIs can mediate many important photochemical and photobiological processes. − …”