Phase control of wavepacket dynamics using shaped femtosecond pulses

Abstract

Coherent vibrational and rotational dynamics of the Li2 molecule is controlled by varying the relative phases, φn, of the rovibrational wavepacket components, ∣n〉 e-i(ωnt+φn). The coherent superposition is created by excitation of a set of ten rovibronic E 1Σg+(νE=12–16, JE=17, 19) states from an intermediate state, A 1Σu+(νA=14, JA=18), using ultrashort optical pulses with well defined spectral amplitudes and phases encoded into the pulse by a liquid crystal spatial light modulator. The wavepacket is probed by time-dependent photoionization and the quantum interference signal is measured as a total ionization yield. The phases of the wavepacket components are optimized to produce partial localization of the wavepacket at a given time t, in specific regions of three-dimensional space defined by the radial and angular coordinates. As a result, the ionization yield, I(t), is maximized or minimized at a time t. The degree of control achieved in the experiment (Imax-Imin)/Imax=64(±12%). The experimental data are interpreted in terms of time-dependent radial and angular probability distributions, calculated for different initial conditions that are determined by the phase relationships in the excitation pulse.