A theoretical investigation of the feasibility of Tannor-Rice type control: Application to selective bond breakage in gas-phase dihalomethanes

Abstract

Within the $\tilde {\rm B}$B̃ absorption band of CH2BrCl, we theoretically analyze the laser-induced control of the Br/Cl branching ratio, Br + CH2Cl ← CH2BrCl → CH2Br + Cl, with CH2BrCl initially in its vibrational ground state. For weak-field excitation, the Br/Cl branching ratio increases as a function of wavelength, however, for wavelengths below 180 nm the branching ratio cannot be made smaller than 0.4. Using optimal control theory, we show that the branching ratio can be made significantly less than 0.4, only when very strong fields are employed. Thus, the present work strongly suggests that a Tannor-Rice type laser control mechanism for selective bond breakage in CH2BrCl cannot take place without accompanying photoionization.

Identifying Strong-Field Effects in Indirect Photofragmentation Reactions

“…8 There has been considerable theoretical and experimental interest in the study of such processes in both diatomic and polyatomic molecular systems. [9][10][11][12][13][14][15][16][17] Photodissociation dynamics can be broadly classified as direct and indirect processes, 7 which can be identified by using a potential energy surface concept. For a direct fragmentation reaction, an excited wavepacket evolves following a purely repulsive potential, from which the molecule can fly apart immediately on an ultrafast time-scale smaller than a typical internal vibrational period.…”

Monotonic convergent quantum optimal control method with exact equality constraints on the optimized control fields

“…Control over the time evolution of quantum systems towards desired quantum states with tailored control fields has motivated extensive experimental and theoretical studies [1][2][3][4][5][6], ranging from the control of chemical reactions [7][8][9][10][11], the performance of gate transformation in quantum information systems [12], to the control in nanostructures [13] and more. While analytically accessible only in highly specialized cases [14], quantum optimal control theory (QOCT) has become a powerful tool for designing optimal control fields that can maximize the control objective [15][16][17][18][19][20].…”

Pulse-train control of photofragmentation at constant field energy

“…20,21 The use of strong fields create, however, potential problems with the population of unwanted channels, e.g., related to ionization. 22 Recently, the weak-field excitation out of a single stationary state has again attracted attention. [23][24][25][26][27][28][29][30] Thus, phase dependence of isomerization yields has been reported recently in the weak-field limit.…”