Field-free alignment dynamics of FCN molecule induced by a terahertz half-cycle pulse

School of Physics and Electronics, Shandong Normal University - Jinan 250358, PRC

^(a) qtmeng@sdnu.edu.cn

Received: 12 November 2018
Accepted: 25 January 2019

Abstract

The molecular alignment induced by external fields is of significance in manipulating a chemical reaction. In this paper, the field-free alignment of a FCN molecule steered by a terahertz (THz) half-cycle laser pulse (HCP) is investigated by solving the density matrix equation. It is shown that a high degree of molecular alignment can be achieved by adjusting the carrier envelope phase (CEP) of the THz HCP. The appearance of a saturation threshold for the molecular alignment by a THz HCP when the field amplitude is increased arises from the 1st-order dipole moment interaction. The effect of the central frequency on the molecular alignment, which is manipulated by a THz HCP, is discussed in detail. By changing the matching number of the THz laser pulse at different CEPs, it is found that under the same conditions, a THz HCP has a certain advantage over a few-cycle laser pulse in improving the FCN molecular alignment. Comparing with a double THz HCP, a better result of the molecular alignment can be obtained by a single THz HCP at the same rotational temperature of molecules.