FEMTOSECOND PUMP-PROBE PHOTOELECTRON-SPECTROSCOPY ON ELECTRONIC STATES OF NA₂: A TOOL TO STUDY ULTRAFAST CONTROL OF CHEMICAL REACTIONS

Abstract

Various one-parameter quantum control schemes applied to Na 2 serve as prototype for current multi-parameter control techniques in order to obtain physical insight into the underlying molecular dynamics.

Weak-field laser phase modulation coherent control of asymptotic photofragment distributions

“…The simplicity of the two conditions required for the laser field used in the present control scheme, namely two pulses that overlap in a certain range of frequencies and with a variable time delay between them, makes this scheme universal and straightforward to apply in current pump-probe experiments of molecular photodissociation processes. In this sense, following the spirit of previous experiments carried out on atomic and diatomic systems, 10,35 a trivial experiment on a polyatomic molecule would consist of applying a pump laser field with two pulses with the same central frequency [i.e., ω 1 = ω 2 in eqn (1)] and the same spectral width (then ensuring 100% of spectral overlap between them), and separated by a ∆t time delay. Thus a wide applicability of the control scheme proposed is envisioned.…”

“…The bandwidth of the laser field composed of the two pulses remains fixed, since it is independent on the time delay between the pulses. It is noted that the possibility of modifying the spectral profile, and therefore the relative populations of the different states excited within a superposition, by varying the time delay between two subsequent pulses has been previously demonstrated experimentally 10,35 and applied theoretically 36 for atomic and diatomic systems using two identical pulses. In this work the above control scheme is applied for the first time to a realistic model of a polyatomic molecule, in order to control the asymptotic final state-resolved photofragment distributions, which are more complex than in diatomic molecules.…”