Background-Free Measurements of Coherent Photoionization by Wavelength-Dependent Femtosecond Probing of a Single Rotational Quantum Beat in the E1Σg+ State of Li2

Published

October 12, 2021

Author(s)

R Uberna, Z Amitay, C X. Qian, S R. Leone

Abstract

The relative coherent ionization yield of lithium dimer is measured quantitatively in a two-color pump-probe femtosecond experiment usingpump pulses around 800 nm and variable-wavelength probe pulses at 508-690. After preparation of a single intermediate rovibronic state witha cw laser, the pump pulse creates a single two-state rotational wave packet by coherent excitation of E ¹Σ_g⁺ (v=9; J=27 and 29). The wavepacket is probed using time-delayed pulses having variable wavelength, with the total energy of the system kept below the dissociation limitof Li₂⁺. The background-free coherent ionization yield (for each probe wavelength) is measured as the relative oscillation amplitude of thesingle quantum beat time-dependent signal. The results closely follow a relatively simple theoretical model, which is based on the assumptionthat the coherent ionization predominantly takes place via the excitation of autoionizing bound singly excited Rydberg states converging to thevarious rovibrational levels of the X²ς_g⁺ ground electronic state of Li₂⁺. An implication of this conclusion is that the final states of the Li₂ system, access by the above probe pulses, can be better approximated by the corresponding set of isolated discrete levels rather than by a continuum.This is highly important in the context of experimental, as well as theoretical, (pump-probe) coherent control and wave packet dynamics studies,in particular, when phase and amplitude shaping of both pump and probe pulses are employed. The results presented here are also the first toinvestigate ionization from around the E ¹ς_g⁺ shelf region of Li₂ with visible light.

Citation

Journal of Chemical Physics

Pub Type

Journals

Keywords

coherent photoionization, femtosecond, Li₂

Citation

Uberna, R. , Amitay, Z. , Qian, C. and Leone, S. (2021), Background-Free Measurements of Coherent Photoionization by Wavelength-Dependent Femtosecond Probing of a Single Rotational Quantum Beat in the E¹Σ_g⁺ State of Li₂, Journal of Chemical Physics (Accessed November 8, 2024)