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Pumping and probing vibrational modulated electronic coherence in HCN by quantum dynamics
van den Wildenberg, Stéphan; Mignolet, Benoît; Remacle, Françoise
2017
 

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Abstract :
[en] Electronic excitation of molecules using few femtoseconds or attoseconds optical pulses can build coherent superpositions of electronic states. A coherent superposition of electronic typically corresponds to a non-stationary electronic density that moves before the onset of nuclear motion, on the few femtoseconds or attosecond timescale. By controlling the parameters of the exciting pulse, it is possible to tailor the non-stationary electron density induced by this pulse. On longer timescale, nuclear motion takes place, and this motion is coupled with the motion of the non-stationary electron density, which opens a way toward control of nuclear dynamics. To achieve this objective, one has to understand how does nuclear motion influences the evolution of the non-stationary electron density by computing the coupled dynamics of electrons and nuclei. In this work, the coupled electronic-nuclear coherent dynamics induced by a short strong VUV fs pulse in the low lying excited electronic states of HCN is probed by transient absorption spectroscopy with a second weaker fs UV pulse. The nuclear time-dependent Schrodinger equation is solved on a 2D nuclear grid with several electronic states with a Hamiltonian including the dipole coupling to the pump and the probe electric fields. The two internal nuclear coordinates describe the motion of the light H atom. There is a band of several excited electronic states at about 8 eV above the ground state (GS) that is transiently accessed by the pump pulse. We tailored the pump so as to selectively populate the lowest 1A” electronic state thereby the pulse creates an electronic coherence with the GS. Our simulations show that this electronic coherence is modulated by the nuclear motion and persists all the way to dissociation on the 1A” state. Transient absorption spectra computed as a function of the delay time between the pump and the probe pulses provide a detailed probe of the electronic amplitude and its phase, as well as of the modulation of the electronic coherence by the nuclear motion, both bound and dissociative.
Disciplines :
Chemistry
Author, co-author :
van den Wildenberg, Stéphan ;  Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de chimie physique théorique
Mignolet, Benoît ;  Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de chimie physique théorique
Remacle, Françoise  ;  Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de chimie physique théorique
Language :
English
Title :
Pumping and probing vibrational modulated electronic coherence in HCN by quantum dynamics
Publication date :
2017
Event name :
Invited seminar at the Instituto de fisica fundamental (Consejo Superior des Investigaciones Cientificas)
Event organizer :
Prof. Octavio Roncero-Villa
Event place :
Madrid, Spain
Event date :
11-10-2017
Available on ORBi :
since 20 January 2020

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