Title: Three-dimensional alignment of asymmetric-top molecules induced by polarization-shaped optimal laser pulses

Journal Article · · Physical Review A
 [1];  [2];  [1]
  1. Tohoku Univ., Sendai (Japan)
  2. Kansas State Univ., Manhattan, KS (United States)
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Optimal control simulation is applied to numerically design nonresonant laser pulses that maximize the degrees of three-dimensional (3D) alignment of SO2 using the lowest-order induced-dipole interaction. In our trials, combinations of more than two mutually orthogonal, linearly polarized subpulses are always obtained as the optimal solutions. Each subpulse in the optimal pulses impulsively excites the rotational wave packet. The optimal pulses effectively cooperate with the rotational dynamics up to only a few partial revival timings owing to the rotational dephasing that determines the effective control periods. The control mechanisms are interpreted in terms of the time derivatives of the expectation values of the squares of the direction cosines, that of the rotational energy, and the interplay between them. We find a special and important role of the last subpulses as they align the molecular axes using the interaction through the two smallest polarizability components, while the other subpulses excite the rotational wave packet mainly through the largest polarizability component. Lastly, the control pulses composed of the specified number of subpulses are also numerically optimized by actively utilizing the instantaneous penalty to systematically show the superiority of the use of more than two subpulses over that of two subpulses, the latter of which leads to the saturation of the degree of 3D alignment as a function of total fluence.

Research Organization:
Kansas State Univ., Manhattan, KS (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Grant/Contract Number:
FG02-86ER13491
OSTI ID:
1610044
Journal Information:
Physical Review A, Journal Name: Physical Review A Journal Issue: 5 Vol. 98; ISSN PLRAAN; ISSN 2469-9926
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Orienting CO molecules with an optimal combination of THz and laser pulses: Optimal control simulation with specified pulse amplitude and fluence journal July 2014
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74 ATOMIC AND MOLECULAR PHYSICS
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