Enantio-conversion of chiral mixtures via optical pumping

Abstract

Enantio-conversion with the help of electromagnetic fields is an essential issue due to the chiralitydependence of many chemical, biological, and pharmaceutical processes. Here, we propose a method for this issue based on a five-level double-∆ model of chiral molecules. By utilizing the breaking of left-right symmetry in the two ∆-type sub-structures, we can establish the chiral-state-selective excitation with one chiral ground state being excited to an achiral excited state and the other one being undisturbed. In the meanwhile, the achiral excited state will relax to the two chiral ground states. The two effects simultaneously acting on the chiral mixtures can convert molecules of different chiralities to the ones of the same chirality, i.e., the enantio-conversion via optical pumping. With typical parameters in gas-phase experiments, we numerically show that highly efficient enantioconversion can be achieved. Our method works in the appearance of decoherences and without the precise control of pulse-durations (pulse-areas) and/or pulse-shapes. These advantages offer it promising features in promoting the future exploring of enantio-conversion. I. INTRODUCTIONRecently, the inner-state enantio-purification [1-19], spatial enantio-separation [20-30], and enantiodiscrimination [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] have become essential issues, since the vast majority of chemical [50], biological [51][52][53], and pharmaceutical [54-57] processes essentially depend on molecular chirality. For these purposes, the (electronic, vibrational, and/or rotational) inner states of chiral molecules are manipulated with the help of electromagnetic fields. Moreover, precisely manipulating the rotational populations of chiral molecules has opened new avenues to study parity violation [58,59].The inner-state enantio-purification includes the enantio-specific state transfer [1-12] and the enantioconversion [13][14][15][16][17][18][19]. It aims to enhance the population excess of one chirality over the other in an inner state in chiral mixtures. The achieved inner-state enantiomeric excess characterizes the efficiency of the inner-state enantiopurification. The enantio-specific state transfer [1][2][3][4][5][6][7][8][9][10][11][12] achieves the enhancement of inner-state enantiomeric excess without changing the chiralities of molecules. The enantio-conversion [13][14][15][16][17][18][19] is more ambitious, since it aims to convert molecules of different chiralities to the ones of the same chirality.Most proposals of the inner-state enantiopurification [1-19] are based on few-level models with left-right symmetry-breaking ∆-type (sub-) structures (e.g. the three-level ∆ type model [1][2][3][4][5][6][7][8][9][10][11][12][13] and the four-level double-∆ [14-19] model). In these models, the chirality-dependency results from the sign difference between the products of the three electric-dipole transition

Complete Controllability Despite Degeneracy: Quantum Control of Enantiomer-Specific State Transfer in Chiral Molecules

“…Denoting the rotational quantum number by J, every energy level of a rigid asymmetric top rotor consists of 2J + 1 states with different values of the orientational quantum number M . While theoretical descriptions of resonant microwave three-wave mixing most often ignore the presence of degenerate energy levels [2,17,19,[21][22][23][24][25], they yield correct predictions on transfer efficiency only for cycles which start from the non-degenerate rotational ground state (J = 0) [20,26,27]. Otherwise, cyclic excitation between three rotational energy levels involves a number of coupled, partially incomplete three-level systems [10][11][12].…”

Enantio-detection via cavity-assisted three-photon processes

“…Molecular chirality has attracted considerable interests due to its fundamental role in the enantio-selective biological activity, chemical reactions, and pharmaceutical processes [1][2][3][4]. The enantio-discrimination [5][6][7][8][9][10][11][12][13][14][15][16][17][18], spatial enantio-separation [19][20][21][22][23][24][25], and inner-state enantiopurification (including the enantio-specific state transfer [26][27][28][29][30][31][32][33][34] and enantio-conversion [35][36][37][38][39][40][41][42]) of chiral molecules are important and challenging tasks. Recently, the investigations have shown the great success in enantio-discrimination of chiral molecules via the enantiomer-specific microwave spectroscopic methods [43][44][45][46]…”

“…Thus, the cavity-molecule(s) system may provide a new platform for the exploration in enantio-discrimination of chiral molecules [61]. Note that the realistic systems for enantio-discrimination [5][6][7][8][9][10][11][12][13][14][15][16][17][18] (or spatial enantio-separation [19][20][21][22][23][24][25] and inner-state enantiopurification [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]) of chiral molecules usually involve a number of molecules. In the cases of many molecules coupled by only the classical light fields [5][6][7][8][9][10][11][12][13]...…”

Evading thermal population influence on enantiomeric-specific state transfer based on a cyclic three-level system via ro-vibrational transitions

“…atomic, molecular, and optical physics . Among these, solely optical (or microwave) methods with the framework of cyclic three-level system (CTLS) [5][6][7] based on electronicdipole transitions, have caught the attention to realize enantioseparation [14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32] as well as enantiodiscrimination [33][34][35][36][37][38][39][40][41][42][43][44][45] and enantioconversion [12][13][14][15][16][17][18].…”