Ultrafast coherent control of giant oscillating molecular dipoles in the presence of static electric fields

Abstract

We propose a scheme to generate electric dipole moments in homonuclear molecular cations by creating, with an ultrashort pump pulse, a quantum superposition of vibrational states on electronic states strongly perturbed by very strong static electric fields. By field-induced molecular stabilization, the dipoles can reach values as large as 50 Debyes and oscillate on a time-scale comparable to that of the slow vibrational motion. We show that both the electric field and the pump pulse parameters can be used to control the amplitude and period of the oscillation, while preventing the molecule from ionizing or dissociating.

Strong field laser control of photochemistry

“…Beyond intensities larger than the TW cm À2 , nonlinear multiphoton transitions may occur. [74][75][76][77] In addition to selective excitation, schemes were conceived to control other molecular properties or functions, such as the adiabatic squeezing of the nuclear wave function, 78 the controlled elongation of the bond distance, as in the laser adiabatic manipulation of the bond (LAMB) scheme [79][80][81][82][83][84][85][86] or the control of intramolecular transitions in the molecule, whether induced by spin-orbit couplings (intersystem crossing) [87][88][89][90] or via nonadiabatic couplings (internal conversion). Static phenomena like bond hardening in a laser-free dissociative state 59 or bond softening of the ground state 60 were first observed and interpreted theoretically through concepts like the light-induced potentials or LIPs.…”

Molecular events in the light of strong fields: A light‐induced potential scenario

“…As the initial state, Wðz; R; 0Þ5uðR; 0Þw BO 1 ðz; RÞ, we consider a nuclear wave function with the same probability density as the ground state of H 2 in the ground electronic state of the ion H 1 2 , essentially assuming an instantaneous ionization process. [96] Since the bond length in H 2 is shorter than in H 1 2 , the ground state of the former is a nuclear wave packet moving in the ground electronic state of the cation, 1r g . An ultrashort pump pulse of s 5 1 fs duration and carrier frequency x p 55:4 eV, with peak amplitude p 50:05 a.u.…”

“…Here, we analyze the role of the electronic wave function and of electron-nuclear dynamics. [96,98,99] In a LAMB process, the total wave function of the system is a coherent superposition of both nuclear and electronic wave functions, [86] WðR; q; tÞ5/ g ðR; tÞN g ðq; RÞ1/ e ðR; tÞN e ðq; RÞ…”

“…In order to analyze the type of electron changes conveyed by the transformation of the LIP and the possible effects of electron-nuclear motion, one needs to use a model that allows integrating the full time-dependent Schr€ odinger equation beyond the Born-Oppenheimer approximation. In the following, we use a well-known 1 1 1D Hamiltonian often employed to characterize the dynamics of the molecular Hydrogen cation under strong fields, [96][97][98][99] H52 h 2 2l e…”

“…In correspondence to the geometrical changes induced by the LIP, there are changes in the electronic properties associated to the electronic superposition state. [96][97][98][99] These properties, for example the permanent or transition dipole, reflect the underlying changes in the redistribution of charges. It was recently shown that some superpositions manifested a clear classical picture of an electron oscillating between the protons, whereas in a dressed electronic state the electron was moving along with the proton.…”