Selective photodissociation in diatomic molecules by dynamical Stark-shift control

Abstract

Selective population transfer in electronic states of dissociative molecular systems is illustrated by adopting a control scheme based on Stark-chirped rapid adiabatic passage (SCRAP). In contrast to the discrete N-level system, dynamical Stark shift is induced in a more complex manner in the molecular electronic states. Wavepacket dynamics on the light-induced potentials, which are determined by the detuning of the pump pulse, can be controlled by additional Stark pulse in the SCRAP scheme. Complete population transfer can be achieved by either lowering the energy barrier along the adiabatic passage or placing the initial wavepacket on a well-defined dressed state suitable for the control. The determination of the pulse sequence is sufficient for controlling population transfer to the target state.

Ultrafast photodissociation assisted by strong non-resonant Stark effect: the ‘straddling’ control pulse

“…In [30], the control mechanism proceeded via adiabatic passage through Stark-shift-induced chirping of the LIPs. We observed different blue-and red-shifting of the photodissociation spectra and selection of a single channel (except at the tails of the maxima of the photospectra).…”

“…In [30] we controlled the photodissociation by adding a low frequency pulse S (t), whose effect on the system dynamics was considered up to the polarizability level. We also neglected the coupling between the two dissociative states and assumed the rotatingwave approximation.…”

“…The main difference of PCOSSE with respect to the application of SCRAP to photodissociation [30] is that in PCOSSE the Stark shift pulse can be constant and it must straddle the pump pulse action, that is, the Stark-shift pulse must precede p (t) and be sustained while p (t) is on. No chirp-induced crossing of the wave packet is under way.…”

“…Recently, we have proposed an extension of the Stark-chirped rapid adiabatic passage scheme [28,29] (SCRAP) using strong pulses to control the yield of a photodissociation reaction involving two excited dissociative electronic states [30]. In particular, we studied the photodissociation of ICl À near or above the threshold of electronic states 2 Å 1/2 and 2 2 Å 1/2 that dissociate into I À þ Cl (in different atomic states of Cl).…”

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

“…[30] However, most works have been done to create the LIAC or LICI in order to control the output of a photochemical process. In particular, there have been several theoretical proposals to control the yield of a photodissociation reaction, [106] as well as the branching ratio over possible fragmentation channels [35,[106][107][108]121] and the kinetic energy distribution of the fragments. [109] Although most proposals remain experimentally untested, owing to the difficulty of finding good molecular systems where the strong field interaction is strong enough to generate LIPs, yet not too strong that the ionization is predominant, recent experiments have shown that indeed such control is possible.…”