Laser control of electronic transitions of wave packet by using quadratically chirped pulses

Abstract

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.

Nonadiabatic Chemical Dynamics: Comprehension and Control of Dynamics, and Manifestation of Molecular Functions

“…Here we consider efficient electronic excitation of wave packet by ultrashort broadband laser pulses, which has fundamental importance in chemical dynamics. The quadratic chirping method formulated in Section V.A.1 is demonstrated to be effective and useful for that also [37]. Although it is possible to use two linearly chirped pulses to control wave packet dynamics [42], it is more efficient to use quadratically chirped pulses.…”

“…Especially when we use a laser field, nonadiabatic transitions are induced among the so-called dressed states and we can control the transitions among them by appropriately designing the laser parameters [33][34][35][36][37][38][39][40][41]. The dressed states mean molecular potential energy curves shifted up or down by the amount of photon energy.…”

“…The dressed states mean molecular potential energy curves shifted up or down by the amount of photon energy. Even the ordinary type of photoexcitation can be nonadiabatic chemical dynamics enhanced very much by appropriately designing the quadratically chirped pulses [36,37,42,43]. Nonadiabatic transitions at naturally existing conical intersections can also be controlled by preparing a wave packet with an appropriate magnitude and direction of momentum.…”

Selective excitation of metastable atomic states by femto- and attosecond laser pulses

“…Because of interference between the crossings, the necessary pulse area of each pulse is much smaller compared to the ARP; however the method is still quite robust. These advantages make the method useful in the field of wave packet control [18]. However, the area of the pulse is still larger than in the case of control by non-chirped pulses.…”

“…The methods from the first group exploit some known physical mechanisms [8,9,10,11,12,13,14,15,16,17,18], e.g., it is possible to introduce some reliable and solvable model equations to estimate the parameters of the controlling laser field analytically, while the methods from the second group are based on the idea of direct variation of the laser field to maximize the desired output [19,20,21,22,23].…”