Eur. Phys. J. D (2014) 68: 355
https://doi.org/10.1140/epjd/e2014-50486-6

Regular Article

Optimal initiation of electronic excited state mediated intramolecular H-transfer in malonaldehyde by UV-laser pulses^*

¹ School of Chemistry, University of Hyderabad, 500 046 Hyderabad, India
² Center for Computational Natural Sciences and Bioinformatics, IIIT Hyderabad, 500 032 Hyderabad, India

^a e-mail: smsc@uohyd.ernet.in

Received: 2 July 2014
Received in final form: 5 September 2014
Published online: 1 December 2014

Abstract

Optimally controlled initiation of intramolecular H-transfer in malonaldehyde is accomplished by designing a sequence of ultrashort (~80 fs) down-chirped pump-dump ultra violet (UV)-laser pulses through an optically bright electronic excited [S₂ (ππ^∗)] state as a mediator. The sequence of such laser pulses is theoretically synthesized within the framework of optimal control theory (OCT) and employing the well-known pump-dump scheme of Tannor and Rice [D.J. Tannor, S.A. Rice, J. Chem. Phys. 83, 5013 (1985)]. In the OCT, the control task is framed as the maximization of cost functional defined in terms of an objective function along with the constraints on the field intensity and system dynamics. The latter is monitored by solving the time-dependent Schrödinger equation. The initial guess, laser driven dynamics and the optimized pulse structure (i.e., the spectral content and temporal profile) followed by associated mechanism involved in fulfilling the control task are examined in detail and discussed. A comparative account of the dynamical outcomes within the Condon approximation for the transition dipole moment versus its more realistic value calculated ab initio is also presented.