Phase control of wavepacket dynamics using shaped femtosecond pulses

Coherent vibrational and rotational dynamics of the Li-2 molecule is contro lled by varying the relative phases, phi(n), of the rovibrational wavepacke t components, \n > e(-i(omega nt+phi n)). The coherent superposition is cre ated by excitation of a set of ten rovibronic E (1)Sigma(g)(+)(nu(E)=12-16, J(E)=17, 19) states from an intermediate state, A (1)Sigma(u)(+)(nu(A)=14, J(A)=18), using ultrashort optical pulses with well defined spectral ampli tudes and phases encoded into the pulse by a liquid crystal spatial light m odulator. The wavepacket is probed by time-dependent photoionization and th e quantum interference signal is measured as a total ionization yield. The phases of the wavepacket components are optimized to produce partial locali zation of the wavepacket at a given time t, in specific regions of three-di mensional 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 deg ree of control achieved in the experiment (I-max-I-min)/I-max=64(+/- 12%). The experimental data are interpreted in terms of time-dependent radial and angular probability distributions, calculated for different initial condit ions that are determined by the phase relationships in the excitation pulse .