Theoretical Study of Dynamic Stark-Induced π-Electron Rotations in Low-Symmetry Aromatic Ring Molecules beyond the Frozen Nuclear Approximation

Abstract

The effects of vibrational motions on dynamic Stark-induced π-electron rotations in a low-symmetry aromatic ring molecule are theoretically studied in the adiabatic approximation. We adopt a simplified three-electronic state model with a few vibronic states. A pair of the lowest vibronic states in two electronic excited states is set degenerate by irradiation of two linearly polarized UV lasers. The resultant degenerate state is named the dynamic Stark-induced degenerate vibronic state (DSIDVS). The laser parameters (intensities and central frequencies) are determined under the conditions of DSIDVS formation. The aromatic ring molecules of interest are supposed to belong to the weak coupling case. The analytical expressions for the DSIDVS and coherent angular momentum L Z (t) are derived in the displaced harmonic oscillator (DHO) model. Two horizontal potential displacements (δ α , δ β ) between the two electronic excited states (α and β) and the ground state are the parameters in the DHO model. The L Z (t) calculated with δ α = δ β is characterized by a regular sequence of the angular momentum pulses with a positive (or negative) constant. For a more general case with δ α ≠ δ β , the regular sequence is broken down because of the contribution of the first excited vibronic state in each electronic state to L Z (t).

Systematic Investigation of the Reliability of the Frozen Nuclei Approximation for Short-Pulse Excitation: The Example of HCCI+

“…The research of charge transfer processes has a relatively long history. While ultrafast charge migration emerged as a hot topic during the past two decades ( Weinkauf et al, 1996 , 1997 ; Remacle et al, 1998 ; Cederbaum and Zobeley, 1999 ; Remacle and Levine, 1999 ; Barth and Manz, 2006 ; Kanno et al, 2006 ; Yudin et al, 2006 ; Remacle et al, 2007 ; Kanno et al, 2010 ; Mineo et al, 2012 ; Calegari et al, 2014 ; Kraus et al, 2015 ; Li et al, 2015 ; Yamaki et al, 2016 ; Wörner et al, 2017 ; Mineo et al, 2021 ). It should be noted that the first attosecond charge migration phenomenon was already introduced in 1944 ( Eyring et al, 1944 ) and was largely forgotten during the next decades.…”

“…For such a short time, the frozen nuclei approximation has been widely used for theoretical work of ultrafast charge migration. There are also several theoretical investigations which include the effects of nuclear motions ( Bandrauk et al, 2009 ; Kanno et al, 2010 ; Ulusoy and Nest, 2012 ; Mendive-Tapia et al, 2013 ; Mineo et al, 2014 ; Despré et al, 2015 ; Mineo et al, 2021 ). The amplitude of charge migration can be significantly modulated by nuclear motions, in particular for relatively long-time dynamics ( Mendive-Tapia et al, 2013 ; Mineo et al, 2014 ; Jia et al, 2019a , b ).…”

Quantum Control of Coherent π-Electron Dynamics in Aromatic Ring Molecules

“…Using laser control, it is also essential to maintain the created ring current at the target region (path) at least during one vibrational period of the PAH [68]. Otherwise, the created ring current would dissipate quickly because of the vibronic interactions and/or the nonadiabatic couplings between the two electronic excited states [30,[69][70][71].…”

“…This paper briefly provides an overview of the theoretical study of quantum laser control of coherent π-electron dynamics in low-symmetry aromatic ring molecules, which we have undertaken in recent several years [39][40][41][42][43][68][69][70][71][72][73]. The essential principles to generate the π-electron angular momentum and ring current in a low symmetry aromatic ring molecule are first to create a superposition of two electronic excited (coherent) states using two linearly polarized lasers, and second to select the clockwise or anticlockwise rotational component from the non-stationary time evolution of the coherent state using pump and dump lasers with properly designed polarization directions.…”

Quantum model of dynamic Stark‐induced degenerate vibronic state by two nonresonant shift‐up lasers for π‐electron angular momentum generation

“…[22] We have recently proposed the effective control scenario for the creation of a unidirectional π-electron rotation in a low-symmetry aromatic ring molecule. [22][23][24][25] Here, vibrational degrees of freedom were not considered. The key point of this scenario was to create a degenerate electronic state of two quasi-degenerate electronic excited states by applying two nonresonant lasers.…”