通过奇偶谐波谱重构不对称平面分子的构型 下载: 705次
1 引言
在过去的20年,原子和分子高次谐波产生[1-2]在强激光与物质相互作用的实验和理论研究中一直是一个热门课题。研究高次谐波的兴趣部分源于其在阿秒科学中的重要应用[3-4],包括电子结构和动力学的阿秒探测[5-6]。可通过三步模型来理解原子分子的高次谐波产生过程[7]:1)电子通过隧穿电离;2)电子在激光场中传播;3)自由电子返回束缚态并伴随高能光子的释放。
近年来,两中心对称分子的高次谐波产生得到广泛研究,如
通过求解含时薛定谔方程的数值方法,详细研究了不同取向角及不同分子构型下三维取向的平面分子
2 数值方法
所研究的三核平面分子
图 1. 三维模拟中平面分子 的坐标系统示意图
Fig. 1. Schematic diagram of coordinate system of planar molecules in 3D simulation
在计算中采用10个周期的激光脉冲,其中3个光学周期是线性上升的,另外7个光学周期保持不变。所采用的激光强度和波长分别为
式中:
3 解析方法
基于强场近似原理[32],由于势的对称性,原子和对称分子仅释放奇次谐波,奇次谐波的产生路径可简单表示为〈p|e⋅r|0〉〈0|e⋅r|p〉r,此公式意味着电子从相同的初始态
不对称分子高次谐波的产生是一个多通道过程,例如本研究中的模型平面分子
式中:
式中:
基于强场近似,沿激光偏振方向相应偶极矩
式中:
4 数值结果和讨论
平面分子
图 2. 三维取向平面分子 的奇偶谐波谱和相应偶极矩的比较。(a) , 的奇偶谐波谱;(b) , 的奇偶谐波谱;(c) , 及 的奇偶偶极矩;(d) , 的奇偶谐波谱;(e) , 的奇偶谐波谱;(f) , 及 的奇偶偶极矩
Fig. 2. Comparison of odd and even harmonic spectra and corresponding dipoles of 3D orientation planar molecules . (a) , odd and even harmonic spectra; (b) , odd and even harmonic spectra; (c) , and odd and even dipoles; (d) , odd and even harmonic spectra; (e) , odd and even harmonic spectra; (f) , and odd and even dipoles
谐波谱和相应偶极矩之间进一步的比较表明:在不同角度下,
可从奇偶高次谐波谱上知道奇偶谐波谱交点的能量
所有干涉项
图 3. 平面等边三角形构型的结果比较
Fig. 3. Comparison of results for planar equilateral triangle configuration
图 4. 平面等腰三角形构型的结果比较
Fig. 4. Comparison of results for planar isosceles triangle configuration
图 5. 平面任意三角形构型的结果比较
Fig. 5. Comparison of results for planar scalene triangle configuration
从
5 结论
综上,利用奇偶谐波谱的交点以及谐波谱与相应偶极矩的关系,在三维空间取向下重构了平面不对称分子
[1] McPherson A, Gibson G, Jara H, et al. Studies of multiphoton production of vacuum-ultraviolet radiation in the rare gases[J]. Journal of the Optical Society of America B, 1987, 4(4): 595-601.
[2] L'Huillier A, Schafer K J, Kulander K C. Theoretical aspects of intense field harmonic generation[J]. Journal of Physics B: Atomic, Molecular and Optical Physics, 1991, 24(15): 3315-3341.
[3] Corkum P B, Krausz F. Attosecond science[J]. Nature Physics, 2007, 3(6): 381-387.
[4] Krausz F, Ivanov M. Attosecond physics[J]. Reviews of Modern Physics, 2009, 81(1): 163-234.
[5] Lépine F, Ivanov M Y, Vrakking M J J. Attosecond molecular dynamics: fact or fiction?[J]. Nature Photonics, 2014, 8(3): 195-204.
[6] Chen J G, Yang Y J, Chen J, et al. Probing dynamic information and spatial structure of Rydberg wave packets by harmonic spectra in a few-cycle laser pulse[J]. Physical Review A, 2015, 91(4): 043403.
[7] Corkum P B. Plasma perspective on strong field multiphoton ionization[J]. Physical Review Letters, 1993, 71(13): 1994-1997.
[8] Lein M, Hay N, Velotta R, et al. Role of the intramolecular phase in high-harmonic generation[J]. Physical Review Letters, 2002, 88(18): 183903.
[9] Li W Y, Dong F L, Yu S J, et al. Ellipticity of near-threshold harmonics from stretched molecules[J]. Optics Express, 2015, 23(24): 31010-31025.
[10] Itatani J, Levesque J, Zeidler D, et al. Tomographic imaging of molecular orbitals[J]. Nature, 2004, 432(7019): 867-871.
[11] Zhou X X, Tong X M, Zhao Z X, et al. Alignment dependence of high-order harmonic generation from N2 and O2 molecules in intense laser fields[J]. Physical Review A, 2005, 72(3): 033412.
[12] Chen Y J, Liu J, Hu B. Reading molecular messages from high-order harmonic spectra at different orientation angles[J]. The Journal of Chemical Physics, 2009, 130(4): 044311.
[13] Chen Y J, Hu B. Role of ionization in orientation dependence of molecular high-order harmonic generation[J]. The Journal of Chemical Physics, 2009, 131(24): 244109.
[14] Li W Y, Wang S, Shi Y Z, et al. Probing the structure of stretched molecular ions with high-harmonic spectroscopy[J]. Journal of Physics B: Atomic, Molecular and Optical Physics, 2017, 50(8): 085003.
[15] Chen Y J, Zhang B. Tracing the structure of asymmetric molecules from high-order harmonic generation[J]. Physical Review A, 2011, 84(5): 053402.
[16] Zhang B, Chen Y J, Jiang X Q, et al. Identifying the interference effect in different harmonic-emission channels from oriented asymmetric molecules[J]. Physical Review A, 2013, 88(5): 053428.
[17] Lu R F, Yu C, Wang Y H, et al. Control of electron localization to isolate and enhance molecular harmonic plateau in asymmetric HeH2+ system[J]. Physics Letters A, 2014, 378(1/2): 90-94.
[18] Pan Y, Zhao S F, Zhou X X. Generation of isolated sub-40-as pulses from gas-phase CO molecules using an intense few-cycle chirped laser and a unipolar pulse[J]. Physical Review A, 2013, 87(3): 035805.
[19] Chen Y J, Fu L B, Liu J. Asymmetric molecular imaging through decoding odd-even high-order harmonics[J]. Physical Review Letters, 2013, 111(7): 073902.
[20] Wu J, Zeng H, Guo C L. Triple-ionization-induced dissociation of NO in strong laser fields[J]. Physical Review A, 2006, 74(3): 031404.
[21] Bian X B, Bandrauk A D. Multichannel molecular high-order harmonic generation from asymmetric diatomic molecules[J]. Physical Review Letters, 2010, 105(9): 093903.
[22] Heslar J, Telnov D, Chu S I. High-order-harmonic generation in homonuclear and heteronuclear diatomic molecules: exploration of multiple orbital contributions[J]. Physical Review A, 2011, 83(4): 043414.
[23] Frumker E, Hebeisen C T, Kajumba N, et al. Oriented rotational wave-packet dynamics studies via high harmonic generation[J]. Physical Review Letters, 2012, 109(11): 113901.
[24] Kraus P M, Rupenyan A, Wörner H J. High-harmonic spectroscopy of oriented OCS molecules: emission of even and odd harmonics[J]. Physical Review Letters, 2012, 109(23): 233903.
[25] Frumker E, Kajumba N, Bertrand J B, et al. Probing polar molecules with high harmonic spectroscopy[J]. Physical Review Letters, 2012, 109(23): 233904.
[26] Yu S J, Zhang B, Li Y P, et al. Ellipticity of odd-even harmonics from oriented asymmetric molecules in strong linearly polarized laser fields[J]. Physical Review A, 2014, 90(5): 053844.
[27] Lötstedt E, Kato T, Yamanouchi K. D3+and H3+in intense laser fields studied with a quasiclassical model[J]. Physical Review A, 2012, 85(5): 053410.
[28] Lefebvre C, Lu H Z, Chelkowski S, et al. Electron-nuclear dynamics of the one-electron nonlinear polyatomic molecule H32+ in ultrashort intense laser pulses[J]. Physical Review A, 2014, 89(2): 023403.
[29] Lötstedt E, Kato T, Yamanouchi K. Classical dynamics of laser-driven D₃⁺[J]. Physical Review Letters, 2011, 106(20): 203001.
[30] Su N, Yu S J, Li W Y, et al. Probing the structure of multi-center molecules with odd-even high harmonics[J]. Chinese Physics B, 2018, 27(5): 054213.
[31] Feit M D, Jr Fleck J A, Steiger A. Solution of the Schrödinger equation by a spectral method[J]. Journal of Computational Physics, 1982, 47(3): 412-433.
[32] Lewenstein M, PhBalcou, CorkumP. B., et al. Theory of high-harmonic generation by low-frequency laser fields[J]. Physical Review A, 1994, 49(3): 2117-2132.
于术娟, 刘竹琴, 刘艳峰, 李雁鹏. 通过奇偶谐波谱重构不对称平面分子的构型[J]. 激光与光电子学进展, 2023, 60(1): 0102002. Shujuan Yu, Zhuqin Liu, Yanfeng Liu, Yanpeng Li. Probing the Structure of Asymmetric Planar Molecules Using Odd-Even High Harmonics[J]. Laser & Optoelectronics Progress, 2023, 60(1): 0102002.