Angular Focusing, Squeezing, and Rainbow Formation in a Strongly Driven Quantum Rotor

Abstract

Semiclassical catastrophes in the dynamics of a quantum rotor (molecule) driven by a strong time-varying field are considered. We show that for strong enough fields, a sharp peak in the rotor angular distribution can be achieved via a time-domain focusing phenomenon, followed by the formation of rainbowlike angular structures. A strategy leading to the enhanced angular squeezing is proposed that uses a specially designed sequence of pulses. The predicted effects can be observed in many processes, ranging from molecular alignment (orientation) by laser fields to heavy-ion collisions, and the trapping of cold atoms by a standing light wave.

Alignment enhancement of molecules embedded in helium nanodroplets by multiple laser pulses

“…We believe the improvement occurs because the time-dependent degree of alignment induced by the first pulse pair reaches a higher value after 18 ps compared to after 10 ps. This is advantageous for the degree of alignment the second pulse pair can induce -see for instance [7,27,28] and the discussion in Sec. IV.…”

“…In a classical model [7,27,28] molecules initially aligned at a polar angle θ 0 with respect to the laser polarization acquire an angular velocity towards the laser polarization of ω(θ 0 ) ∝ sin 2θ 0 after the pulse if zero initial angular velocity is assumed. When the second kick pulse is sent while the molecules rotate towards the kick pulse polarization the angular speed will increase and peak alignment is reached faster.…”

Colloquium: Aligning molecules with strong laser pulses

“…During the past few years the field of intense laser alignment has been growing rapidly, with an ever increasing number of contributions from both experimental Felker, 1996, 1997;Larsen et al, 1998Larsen et al, , 2000Sakai, Safvan, 1998;Lappas and Marangos, 2000;Baumfalk, Nahler, and Buck, 2001;Rosca-Pruna and Vrakking, 2001, 2002a, 2002bVelotta et al, 2001;Bartels et al, 2002;Poulsen, Skovsen, and Stapelfeldt, 2002;Sakai et al, 2002) and theoretical (Friedrich and Herschbach, 1995aSeideman, 1995bSeideman, , 1999aSeideman, , 1999bSeideman, , 2001aSukharev and Krainov, 1998;Andryushin and Fedorov, 1999;Dion, Bandrauk, Atabek, Keller, Umeda, and Fujimura, 1999;Henriksen, 1999;Ortigoso et al, 1999;Yan and Seideman, 1999;Keller, Dion, and Atabek, 2000;Larsen et al, 2000;Legare, Chelkowski, and Bandrauk, 2000;Averbukh and Arvieu, 2001;Cai, Marango, and Friedrich, 2001;Dion, Keller, and Atabek, 2001;Hoki and Fujimura, 2001;Machholm, 2001;Machholm and Henriksen, 2001;Dion et al, 2002;Guerin et al, 2002;Kalosha et al, 2002;Van Leuven, Malvaldi, and Persico, 2002) research. Recent work has analyzed the role played by various system...…”

Observation of the field-free orientation of a symmetric-top molecule by terahertz laser pulses at high temperature

“…At low temperature, a very high degree of orientation can be obtained using such control strategies and a molecular quantum-state selection [32,33,34,35]. Control schemes in the sudden regime, where the duration of the control field is short with respect to the rotational period, have been also developed [36,37,38,39,40,12,41,42,43,44,45,46,47,48,49,50,51,52]. Among other techniques, we can mention the interaction of the molecule with a terahertz (THz) laser pulse and the (ω, 2ω)-scheme.…”