The title theory is developed by combining the Herman-Kluk semiclassical theory for adiabatic propagation on single potential-energy surface and the semiclassical Zhu-Nakamura theory for nonadiabatic transition. The formulation with use of natural mathematical principles leads to a quite simple expression for the propagator based on classical trajectories and simple formulas are derived for overall adiabatic and nonadiabatic processes. The theory is applied to electronically nonadiabatic photodissociation processes: a one-dimensional problem of H2+ in a cw (continuous wave) laser field and a two-dimensional model problem of H2O in a cw laser field. The theory is found to work well for the propagation duration of several molecular vibrational periods and wide energy range. Although the formulation is made for the case of laser induced nonadiabatic processes, it is straightforwardly applicable to ordinary electronically nonadiabatic chemical dynamics.

An effective scheme is proposed for the laser control of wave packet dynamics. It is demonstrated that by using specially designed quadratically chirped pulses, fast and nearly complete excitation of wave packet can be achieved without significant distortion of its shape. The parameters of the laser pulse can be estimated analytically from the Zhu-Nakamura theory of nonadiabatic transition. If the wave packet is not too narrow or not too broad, then the scheme is expected to be utilizable for multidimensional systems. The scheme is applicable to various processes such as simple electronic excitation, pump-dump, and selective bond breaking, and it is actually numerically demonstrated to work well by taking diatomic and triatomic molecules (LiH, NaK, H(2)O) as examples.

In the present paper semiclassical formulation of optimal control theory is made by combining the conjugate gradient search method with new approximate semiclassical expressions for correlation function. Two expressions for correlation function are derived. The simpler one requires calculations of coordinates and momenta of classical trajectories only. The second one requires extra calculation of common semiclassical quantities; as a result additional quantum effects can be taken into account. The efficiency of the method is demonstrated by controlling nuclear wave packet motion in a two-dimensional model system. Keywords:optimal control theory, laser control, semiclassical approximation Controlling molecular processes by laser pulses is a subject of active research in physics. One of the most natural and flexible approaches in this area is the optimal control theory (OCT) [1,2]. It is based on the idea that the controlling laser pulse should maximize a certain functional so that the variational principle can be used to design the pulse. The procedure leads to a set of equations for optimal laser field, which includes two Schrodinger equations to describe the dynamics starting from the initial and target state wave packets. The optimal laser field is given by the imaginary part of the correlation function of these two wave packets. This system of equations of optimal control must be solved iteratively in general.During the last 20 years a number of methods based on this idea have been developed [3][4][5][6][7][8][9]. The earliest formulations of the problem for classical [3][4][5][6] and quantum [7] systems employ the well established numerical conjugate gradient search method to solve the system of equations iteratively and maximize the certain functional. Later the more effective numerical schemes to solve this system of optimal control equations have been introduced [8,9]. These iterative algorithms converge faster than the gradient-type.In all these approaches the optimal laser field is given by the imaginary part of a certain correlation function. In the simple case of quantum conjugate gradient search method [7] this function has the form where |φ(t) and |χ(t) are the wave packets driven by the optimal field starting from different initial states and µ(r) is the dipole moment. To calculate the optimal field two Schrodinger equations for |φ(t) and |χ(t) together with the equation for correlation function (1) should be solved iteratively in general; hence its numerical cost becomes huge for multi-dimensional systems.Since the quantum OCT is limited to low-dimensional systems because of formidable numerical cost, it is strongly desired to incorporate semiclassical approaches of wave packet propagation like the HermanKluk method [10,11] into the OCT. Within the semiclassical approach each wave packet is formed by summation of contributions from a large number of classical trajectories. In order to calculate the correlation function the double summation with respect to this large number of trajectories ...

The influence of laser-induced continuum structure on the angular distribution of photoelectrons is studied in the femtosecond time domain by direct numerical solution of the time-dependent Schrödinger equation. Control of the photoelectron angular distribution is demonstrated for the hydrogen atom by coherent population transfer from the initial S-state to an excited D-state via the p-continuum and further ionization into the f-continuum states. A direct optimization procedure is used to find a domain of laser parameters, for which the efficiency of the control with respect to the time delay and energy detuning between the laser pulses is maximized.