Tracing the structure of asymmetric molecules from high-order harmonic generation

Abstract

We investigate high-order harmonic generation (HHG) from asymmetric molecules exposed to intense laser fields. We show that the emissions of odd and even harmonics depend differently on the orientation angle, the internuclear distance, as well as the effective charge. This difference mainly comes from different roles of intramolecular interference in the HHG of odd and even harmonics. These roles map the structure of the asymmetric molecule to the odd vs even HHG spectra.

Probing the structure of multi-center molecules with odd–even high harmonics

“…[16][17][18][19][20][21][22][23][24] It can be used to probe the internuclear distance of the diatomic molecule [25][26][27][28] and judge the sign of the dipole phase in the molecular orbital tomography procedure. [12] For asym-metric diatomic molecules, such as HeH 2+ , [29][30][31][32][33][34][35][36][37][38] CO, [39][40][41][42][43] and NO, [44] due to symmetry breaking, both odd and even harmonics are emitted. It has been shown that these odd and even harmonics possess different spectral properties [45][46][47][48] and carry different information of the target, [31,[49][50][51] and therefore need to be studied separately.…”

“…[12] For asym-metric diatomic molecules, such as HeH 2+ , [29][30][31][32][33][34][35][36][37][38] CO, [39][40][41][42][43] and NO, [44] due to symmetry breaking, both odd and even harmonics are emitted. It has been shown that these odd and even harmonics possess different spectral properties [45][46][47][48] and carry different information of the target, [31,[49][50][51] and therefore need to be studied separately.…”

Role of the Coulomb potential on the ellipticity in atomic high-order harmonics generation

“…When atoms and molecules are exposed to intense laser irradiation, high-order harmonics (HH) will be generated. The high-order harmonic generation (HHG) has been an attractive topic for the past two decades for its potential application of producing coherent attosecond pulses [1][2][3][4][5][6][7] in the XUV regime and self-probing of molecules allowing a combination of attosecond and Ångström resolutions [8][9][10][11][12]. The physical mechanism of HHG can be understood by the threestep model: (i) an atom or molecule emits its electron to continuous state, (ii) the electron is accelerated in the laser field, (iii) the accelerated electron recombines with the parent ion and high energy photon is radiated [13,14].…”

Advances on odd-even high-harmonic spectroscopy

“…此外, 由于波函数没有确定宇称, 使得不对称分子在单色激光 场中辐射的谐波既包含奇次又包含偶次. 通过将奇次和 偶次谐波分开独立研究, 近期的理论工作 [35] 指出, 奇偶 谐波辐射在频域上具有显著不同的特性. 通过建立奇偶 谐波辐射理论模型, 进一步的理论研究 [35,36] 表明, 奇偶 [36] 、探 测不对称分子瞬时结构 [38,39] 、追踪电子动力学 [40] 、探 测核的动力学 [41] 、标定取向度 [42] 、探测多中心分子结 构 [43] 和探测同位素效应 [44] 等.…”