1
|
Ortmann L, AlShafey A, Staudte A, Landsman AS. Tracking the Ionization Site in Neutral Molecules. PHYSICAL REVIEW LETTERS 2021; 127:213201. [PMID: 34860111 DOI: 10.1103/physrevlett.127.213201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 09/19/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Abstract
When a diatomic molecule is exposed to intense light, the valence electron may tunnel from a higher potential (corresponding to an upfield atom) due to the suppressed internuclear barrier. This process is known as ionization enhancement and is a key mechanism in strong field ionization of molecules. Alternatively, the bound electron wave function can evolve adiabatically in the laser field, resulting in ionization from the downfield atom. Here, we introduce a method to quantify the relative contribution of these two processes. Applying this method to experimentally measured electron momenta distributions following strong field ionization of N_{2} with infrared laser light, we find approximately a 2∶1 ratio of electrons ionized from a downfield atom, relative to upfield. This suggests that the bound state wave function largely adapts adiabatically to the changing laser field, although the nonadiabatic process of ionization enhancement still contributes even in neutral molecules. Our method can be applied to any diatomic neutral molecule to better understand the evolution of the initially bound electron wave packet and hence the nature of the molecular ionization process.
Collapse
Affiliation(s)
- L Ortmann
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, D-01187 Dresden, Germany
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - A AlShafey
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - A Staudte
- Joint Attosecond Science Lab of the National Research Council and the University of Ottawa, Ottawa, Ontario K1A 0R6, Canada
| | - A S Landsman
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| |
Collapse
|
2
|
Affiliation(s)
- Kazuo Takatsuka
- Fukui Institute for Fundamental Chemistry, Kyoto University, 606-8103 Kyoto, Japan
| | - Yasuki Arasaki
- Fukui Institute for Fundamental Chemistry, Kyoto University, 606-8103 Kyoto, Japan
| |
Collapse
|
3
|
Barborini M, Sorella S, Rontani M, Corni S. Angle-resolved photoemission spectroscopy from first-principles quantum Monte Carlo. J Chem Phys 2018; 149:154102. [DOI: 10.1063/1.5038864] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
| | - Sandro Sorella
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy
| | | | - Stefano Corni
- CNR-NANO, Via Campi 213/a, 41125 Modena, Italy
- Dipartimento di Scienze Chimiche—Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| |
Collapse
|
4
|
Yuan H, He L, Wang F, Wang B, Zhu X, Lan P, Lu P. Tomography of asymmetric molecular orbitals with a one-color inhomogeneous field. OPTICS LETTERS 2018; 43:931-934. [PMID: 29444030 DOI: 10.1364/ol.43.000931] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 01/19/2018] [Indexed: 06/08/2023]
Abstract
We demonstrate image asymmetric molecular orbitals via high-order harmonic generation in a one-color inhomogeneous field. Due to the broken inversion symmetry of the inhomogeneous field in space, the returning electrons with energy in a broad range can be forced to recollide from only one direction for all the orientation angles of molecules, which therefore can be used to reconstruct asymmetric molecular orbitals. Following the procedure of molecular orbital tomography, the highest occupied molecular orbital of carbon monoxide (CO) is satisfactorily reconstructed with high-order harmonic spectra driven by the inhomogeneous field. This scheme is helpful to relax the requirement of laser conditions and is also applicable to other asymmetric molecules.
Collapse
|
5
|
Wang B, He L, Wang F, Yuan H, Zhu X, Lan P, Lu P. Resonance enhanced high-order harmonic generation in H2+ by two sequential laser pulses. OPTICS EXPRESS 2017; 25:17777-17787. [PMID: 28789269 DOI: 10.1364/oe.25.017777] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 06/30/2017] [Indexed: 06/07/2023]
Abstract
We investigate high-order harmonic generation in H2+ by using two sequential laser pulses, which consist of a 800-nm pump pulse and a time-delayed 1600-nm probe pulse. Based on the solution of the time-dependent Schrödinger equation, we demonstrate that the harmonic cutoff in our two-pulse scheme is significantly extended compared to that in the 1600-nm probe pulse alone. Meanwhile, the harmonic efficiency is enhanced by 2-3 orders of magnitude due to charge-resonance-enhanced ionization steered by the 800-nm pump pulse. By using a probe pulse with longer wavelength, our scheme can be used for efficient high harmonic generation in the water window region. In addition, the influence of the intensity of the pump pulse and the relative time delay of the two laser pulses on the harmonic generation are also investigated.
Collapse
|
6
|
Li Y, Li M, Zhou Y, Ma X, Xie H, Lan P, Lu P. Carrier-envelope phase dependent photoelectron energy spectra in low intensity regime. OPTICS EXPRESS 2017; 25:11233-11243. [PMID: 28788805 DOI: 10.1364/oe.25.011233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We study the carrier-envelope phase (CEP) dependent photoelectron energy spectra from above-threshold ionization by numerically solving the time-dependent Schrödinger equation of hydrogen atom in a few-cycle laser field at intensities in the range of (2-10) × 1013 W/cm2. Depending on the electron energy and the laser intensity, the yield of the photoelectron reveals clear oscillations with respect to the CEP. At high laser intensities (larger than ~3 × 1013 W/cm2), the yield of the high-energy photoelectrons (larger than 2Up, with Up being the ponderomotive potential) shows two kinds of oscillations with the CEP for different electron energies. There is a clear phase jump for those two kinds of oscillations. In contrast, at low laser intensities (smaller than ~3 × 1013 W/cm2), the phase of the oscillation for the high-energy photoelectron yield with the CEP is nearly independent on the electron energy, which will reduce the sensitivity of the retrieval of single-shot CEP using the method reported by T. Wittmann et al. [Nat. Phys. 5, 357 (2009)] at low laser intensities. We further show that the low-energy photoelectrons display distinct CEP-dependent intercycle interference fringes, providing an alternative approach to retrieve the CEP with high sensitivity in a few-cycle laser field with low intensity.
Collapse
|
7
|
Zhou Y, Li M, Li Y, Tong A, Li Q, Lu P. Dissection of electron correlation in strong-field sequential double ionization using a classical model. OPTICS EXPRESS 2017; 25:8450-8458. [PMID: 28380956 DOI: 10.1364/oe.25.008450] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Recent experiments on strong-field sequential double ionization (SDI) have reported several observations which are regarded as evidence of electron correlation, querying the validity of the standard independent electron approximation for SDI. Here we theoretically study SDI with a classical ensemble model. The experimental results are well reproduced with this model. Back tracing of the ionization process shows that these results are ascribed to the subcycle ionization dynamics of the two electrons, not the evidences of the electron correlation in SDI. Thus, the previously reported observations are not enough to claim the breakdown of the independent electron approximation in SDI.
Collapse
|
8
|
Zhang X, Zhu X, Liu X, Wang D, Zhang Q, Lan P, Lu P. Ellipticity-tunable attosecond XUV pulse generation with a rotating bichromatic circularly polarized laser field. OPTICS LETTERS 2017; 42:1027-1030. [PMID: 28295083 DOI: 10.1364/ol.42.001027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We propose and theoretically demonstrate a method to generate attosecond XUV pulses with tunable ellipticity from aligned molecules irradiated by a bichromatic counterrotating circularly polarized (BCCP) driving laser field. By rotating the BCCP field, the attoseond XUV pulse varies from being left elliptically polarized to right elliptically polarized. The rotation of the BCCP field can be easily achieved by adjusting the relative phases between the two circularly polarized components. This scheme will benefit a broad range of applications, including the exploration of chiral-sensitive properties of the light-matter interaction and time-resolved imaging of magnetic structures.
Collapse
|
9
|
Wang Z, Li M, Zhou Y, Lan P, Lu P. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule. Sci Rep 2017; 7:42585. [PMID: 28218294 PMCID: PMC5316950 DOI: 10.1038/srep42585] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 01/12/2017] [Indexed: 11/30/2022] Open
Abstract
The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.
Collapse
Affiliation(s)
- Zhuo Wang
- School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Min Li
- School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yueming Zhou
- School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Pengfei Lan
- School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Peixiang Lu
- School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
- Laboratory of Optical Information Technology, Wuhan Institute of Technology, Wuhan 430205, China
| |
Collapse
|
10
|
Xie H, Li M, Li Y, Zhou Y, Lu P. Intra-half-cycle interference of low-energy photoelectron in strong midinfrared laser fields. OPTICS EXPRESS 2016; 24:27726-27737. [PMID: 27906341 DOI: 10.1364/oe.24.027726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Using semiclassical models with implementing interference effects, we study the low-energy photoelectron intra-half-cycle interferences among nonscattering trajectories and multiple forward scattering trajectories of atoms ionized by a strong mid-infrared laser field. Tracing back to the initial tunneling coordinates, we find that up to three kinds of forward scattering trajectories have substantial contributions to the low-energy photoelectrons. Those multiple forward scattering trajectories depend sensitively on the initial transverse momentum at the tunnel exit and they lead to sign reversal of the transverse momentum of the electrons. We show that the interference of the nonscattering trajectory and the triple-scattered trajectory has the largest contribution to the low-energy structure in mid-infrared laser fields. It is also shown that the long-range Coulomb potential has a significant effect on the low-energy photoelectron interference patterns.
Collapse
|