Time-resolved photoelectron spectroscopy of proton transfer in the ground state of chloromalonaldehyde: Wave-packet dynamics on effective potential surfaces of reduced dimensionality

Abstract

We report on a simple but widely useful method for obtaining time-independent potential surfaces of reduced dimensionality wherein the coupling between reaction and substrate modes is embedded by averaging over an ensemble of classical trajectories. While these classically averaged potentials with their reduced dimensionality should be useful whenever a separation between reaction and substrate modes is meaningful, their use brings about significant simplification in studies of time-resolved photoelectron spectra in polyatomic systems where full-dimensional studies of skeletal and photoelectron dynamics can be prohibitive. Here we report on the use of these effective potentials in the studies of dump-probe photoelectron spectra of intramolecular proton transfer in chloromalonaldehyde. In these applications the effective potentials should provide a more realistic description of proton-substrate couplings than the sudden or adiabatic approximations commonly employed in studies of proton transfer. The resulting time-dependent photoelectron signals, obtained here assuming a constant value of the photoelectron matrix element for ionization of the wave packet, are seen to track the proton transfer.

Quantum wavepacket dynamics for time-resolved photoelectron spectroscopy of the NO2 conical intersection

“…Photoelectron angular distributions offer more direct information of the character of electronic states involved. In particular, we have previously investigated the use of time-resolved photoelectron spectra in tracking several fundamental types of dynamics: vibration across one-dimensional double well potential in an excited state of Na 2 [3,4], photoelectron spectra reflecting real-time nonadiabatic dynamics of wavepackets undergoing bifurcation at an avoided crossing in NaI molecule [5,6], and for observing ground state proton transfer in chloromalonaldehyde [7][8][9].…”

The exact forces on classical nuclei in non-adiabatic charge transfer

“…Prominent examples of such electronic non-adiabatic processes appear throughout physics, chemistry and biology, for example, vision, [2][3][4] photosynthesis, 5,6 photo-voltaics, [7][8][9] and proton-transfer/hydrogen storage. [10][11][12][13] The standard approaches to describe non-adiabatic molecular processes are in terms of coupled BOPESs and transitions between the corresponding adiabatic electronic states induced by the nuclear motion. In the Born-Huang expansion, the exact solution of the time-dependent Schrödinger equation (TDSE) is expanded in the complete set of BO electronic states, leading to a nuclear wave packet with contributions on several BOPESs that undergo transitions in the regions of strong non-adiabatic coupling.…”

Time-resolved photoelectron spectroscopy of wavepackets through a conical intersection in NO2

“…We have previously demonstrated the utility of such time-resolved photoelectron angular distributions and the need to incorporate geometry-and energy-dependent photoionization matrix elements in studies of time-resolved photoelectron spectra in a series of papers tracking funda-mental wavepacket dynamics in different scenarios: vibrational motion across a one-dimensional double-well potential in an excited state of Na 2 , [24][25][26][27][28] wavepacket bifurcation at an avoided crossing in NaI, 29,30 and proton transfer in the ground state of chloromalonaldehyde. [31][32][33] The scheme for our studies of the pump-probe photoelectron spectra in NO 2 is illustrated in Fig. 1.…”