Scoring molecular wires subject to an ultrafast laser pulse for molecular electronic devices

• Published in: Journal of computational chemistry Vol. 44; no. 21; pp. 1776 - 1785
• Main Authors: Lu, Hui, Azizi, Alireza, Mi, Xiao Peng, Wenjing, Yu, Peng, Yuting, Xu, Tianlv, Früchtl, Herbert, Mourik, Tanja, Kirk, Steven R., Jenkins, Samantha
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.08.2023; Wiley Subscription Services, Inc
• Subjects: Critical point; Electron states; Electronic devices; Electrons; Ethylene; Lasers; Quantum theory; Ultrafast lasers
• ISSN: 0192-8651; 1096-987X; 1096-987X
• DOI: 10.1002/jcc.27126

A nonionizing ultrafast laser pulse of 20‐fs duration with a peak amplitude electric‐field ±E = 200 × 10−4 a.u. was simulated. It was applied to the ethene molecule to consider its effect on the electron dynamics, both during the application of the laser pulse and for up to 100 fs after the pulse was switched off. Four laser pulse frequencies ω = 0.2692, 0.2808, 0.2830, and 0.2900 a.u. were chosen to correspond to excitation energies mid‐way between the (S1,S2), (S2,S3), (S3,S4) and (S4,S5) electronic states, respectively. Scalar quantum theory of atoms in molecules (QTAIM) was used to quantify the shifts of the C1C2 bond critical points (BCPs). Depending on the frequencies ω selected, the C1C2 BCP shifts were up to 5.8 times higher after the pulse was switched off compared with a static E‐field with the same magnitude. Next generation QTAIM (NG‐QTAIM) was used to visualize and quantify the directional chemical character. In particular, polarization effects and bond strengths, in the form of bond‐rigidity vs. bond‐flexibility, were found, for some laser pulse frequencies, to increase after the laser pulse was switched off. Our analysis demonstrates that NG‐QTAIM, in partnership with ultrafast laser irradiation, is useful as a tool in the emerging field of ultrafast electron dynamics, which will be essential for the design, and control of molecular electronic devices. Main: The time variation of the population of the S0, S3, and S6 electronic states that are nonzero, with time. Inset‐top: The ethene bond‐path framework set B displaying the {q (magenta), q′ (red)} path‐packets for a laser pulse frequency ω = 0.290 au corresponding to the peak Ex‐field value: Ex = −199.7 × 10−4 a.u at a time 9.823 fs. Inset‐middle: The corresponding {q, q′} path‐packets for Ex = +199.6 × 10−4 a.u. at a time 10.083 fs. Inset‐bottom: The {q, q′} path‐packets at 100 fs after the pulse is switched off.