Excitation and ionization of molecular hydrogen by ultrashort vuv laser pulses

We report calculations for excitation and ionization of the hydrogen molecule by using ultrashort vuv laser pulses. The theoretical method is based on the solution of the time-dependent Schrodinger equation in a basis of stationary molecular states that includes all electronic and vibrational degrees of freedom. We show that the use of femtosecond vuv pulses, i. e., of pulses with a duration comparable to that of the molecular vibrational period, can be used to efficiently manipulate the molecular response by constraining the nuclear motion to a desired time interval. Thus it is possible to control the ratio of dissociative to nondissociative ionization and the final H-2(+) vibrational distribution and, by increasing the laser intensity, to induce stepladder Rabi oscillations that can populate excited electronic states not accessible by direct photon absorption. A precise theoretical description of all these effects can only be achieved by including the vibrational motion during the time evolution.