Control of photodissociation with the dynamic Stark effect induced by THz pulses

Abstract

We demonstrate how dynamic Stark control (DSC) can be achieved on molecular photodissociation in the dipole limit, using single-cycle (FWHM) laser pulses in the terahertz (THz) regime. As the laser-molecule interaction follows the instantaneous electric field through the permanent dipoles, the molecular potentials dynamically oscillate and so does the crossings between them. In this paper, we consider rotating-vibrating diatomic molecules (2D description) and reveal the interplay between the dissociating wave packet and the dynamically fluctuating crossing seam located in the configuration space of the molecules spanned by the R vibrational and θ rotational coordinates. Our showcase example is the widely studied lithium-fluoride (LiF) molecule for which the two lowest Σ states are nonadiabatically coupled at an avoided crossing (AC), furthermore a low-lying pure repulsive Π state is energetically close. Optical pumping of the system in the ground state thus results in two dissociation channels: one indirect route via the AC in the ground Σ state and one direct path in the Π state. We show that applying THz control pulses with specific time delays relative to the pumping, can significantly alter the population dynamics, as well as, the kinetic energy and angular distribution of the photofragments.

Unraveling photodissociation dynamics by sub-femtosecond ultraviolet pulses: insights into fragmental kinetics and carrier-envelope phase characterization

“…While intense femtosecond UV pulses have sparked theoretical interest in photodissociation dynamics [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], scant research has delved into the impact of pulse duration on this process. Our focus is on the consequences of varying pulse duration-ranging from hundreds of femtoseconds to sub-femtoseconds-initiated by 'resonant' weak UV pulses, specifically exploring kinetic energy release (KER) spectra in diatomic molecules.…”

Attosecond Probing of Nuclear Vibrations in the D2+ and HeH+ Molecular Ions

“…Most of the probing techniques are customized to monitor molecular motion in excited states after optical or (X)­UV pumping. In general, it is more difficult to induce significant structural changes in the ground electronic state using pulsed laser excitation. , The dynamic Stark control (DSC) of potential energy surfaces is often applied to prepare initial wave packets and manipulate the nuclear wave packet motion − or the photoexcitation probability . In this regard, simple polar diatomic molecules with large permanent dipoles, like HeH + , are important showcase systems for studying DSC-related processes.…”

Light-induced photodissociation in the lowest three electronic states of the NaH molecule

“…There are a large number of theoretical and experimental works available which have been devoted to discussing numerous new phenomena of light–matter interaction. Although many of these works treat the dynamical problem of diatomics starting investigations from the simplest hydrogen-like ions or molecules to systems with large numbers of electrons, 1–16 other relevant papers are tackling the problem of photodissociation and fragmentation of polyatomics, as well. 17–36…”