Programme

P.60 -- Poster, VCTP-46

Date: Wednesday, 6 October 2021

Time: 08:30 - 10:00

Probing the permanent dipole moment of polar molecule from high-oder harmonic generation

Kim-Ngan H. Nguyen(1), Ngoc-Loan Phan(1), Cam-Tu Le(2), Van-Hoang Le(1)

(1) Ho Chi Minh City University of Education, Ho Chi Minh City, Vietnam; (2)Ton Duc Thang University, Ho Chi Minh City, Vietnam

When an atom or symmetric molecule interacts with the ultrashort intense laser pulse, they emit high-order harmonics with only odd order. Meanwhile, for the polar molecules characterized by their permanent dipole, the HHG possesses both odd and even harmonics [1-2]. Our previous study [3] examined the ratio between adjacent even and odd harmonics (called the even-to-odd ratio) in relationship with the permanent dipole moment. We have found that the even-to-odd ratio strongly depends on the nuclear-charge ratio of the two molecular nuclei and the permanent molecular dipole. In addition, we have pointed out that the found dependence has the form of hysteresis curves. This sensitivity of the even-to-odd ratio to the permanent molecular dipole suggests developing a tool to extract permanent molecular dipole from the odd-even HHG data. For this purpose, first, we theoretically approach the task by simulating the HHG spectra from diatomic asymmetric molecules using the numerical method of solving the time-dependent Schrödinger equation. For simplicity, we use the $Z_1Z_2$ model of polar molecules. Afterward, we investigate the HHG spectra of a polar molecule with different intramolecular distances and, thus, diverse permanent dipole moments. We expect to find a relationship between the even-to-odd ratio and the permanent dipole moments. We will also examine the stability of this relation on various parameters of the laser pulses. Finally, using the found relationship, we extract the permanent dipole from the HHG data and examine the validity of the method by comparing it with the initial input data while simulating the HHG spectra. Reference [1] P. M. Kraus, A. Rupenyan, and H. J. Wörner, “High-harmonic spectroscopy of oriented OCS molecules: Emission of even and odd Harmonics”, Phys. Rev. Lett. 109, 233903 (2012). [2] N. L. Phan, C. T. Le, V. H. Hoang, and V. H. Le, “Odd-even harmonic generation from oriented CO molecules in linearly polarized laser fields and the influence of the dynamic core-electron polarization”, Phys. Chem. Chem. Phys. 21, 24177 (2019). [3] Kim-Ngan Nguyen-Huynh, Cam-Tu Le, Hien T. Nguyen, Lan-Phuong Tran, Ngoc-Loan Phan, “Effect of molecular charge asymmetry on even-to-odd ratio of high-order harmonic generation”, Communications in Physics 30, No. 3, pp. 197-208 (2020).

Presenter: Nguyen Huynh Kim Ngan