Real-Time Observation of Electron-Hole Coherence Induced by Strong-Field Ionization

Abstract

We introduce and demonstrate a new approach to measure the electron-hole dynamics and coherence induced by strong-field ionization using hole-assisted high-harmonic spectroscopy. The coherent driving of the infrared and XUV pulses correlates the dynamics of the core-hole and the valence-hole by coupling multiple continua, which leads to the otherwise forbidden absorption and emission of high harmonics. An analytical model is developed based on the strong-field approximation by taking into account of the essential multielectron configurations. The emission spectra from the core-valence transition and the core-hole recombination are found modulating strongly as functions of the time delay between the two pulses, suggesting the coherent electron wave packets in multiple continua can be utilized to temporally resolve the core-valence transition in attoseconds.

Tracking Charge Migration with Frequency-Matched Strobo-Spectroscopy

“…Understanding the ultrafast motion of electrons within matter is of critical importance in many areas of science and technology. One example is charge migration − (CM): the coherent motion of a positively charged electron hole along the backbone of a molecule following a localized ionization event, which can be observed on Angstrom spatial scales and attosecond time scales. − CM is a widely studied phenomenon due to its potential for understanding and perhaps steering downstream processes such as chemical reactions, photosynthesis, and photovoltaics via charge-directed reactivity. − Since its discovery in the late 1990s, , the study of CM has flourished, ,− with much of this research performed in recent years. − …”

Calibration of quantitative rescattering model for simulating vortex high-order harmonic generation driven by Laguerre–Gaussian beam with nonzero orbital angular momentum

“…[8][9][10][11] While it is relatively straightforward to generate vortex light beams with nonzero OAM by optical elements in the infrared (IR) and visible ranges, [12] similar technology is much more difficult to create vortex beams in the extreme ultraviolet (XUV) and soft x-rays (SXR). [13] However, as a wellknown strong-field phenomenon, [14][15][16][17] using high-order harmonic generation (HHG) from gaseous medium, i.e., an upconversion nonlinear process, the OAM beam can be converted from the IR to the XUV and SXR. [18][19][20][21][22][23][24][25][26][27][28] For instance, in the first experiment, in 2012, Zürch et al [18] measured low-charged XUV vortices whose topological charges do not scale with the harmonic order.…”

Modulation of High-Order Harmonic Generation from a Monolayer ZnO by Co-rotating Two-Color Circularly Polarized Laser Fields

“…In the past decade, a large number of theoret-ical and experimental studies related to HHG have been carried out for series of solid materials with different band gaps and properties. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] Among them, two-dimensional crystal materials have become popular target for solid high-order harmonics due to their unique electronic structure, excellent optical properties, strong electron-electron interaction, and negligible propagation effects. [49,50] In addition, polarization characteristics of high-order harmonics of two-dimensional materials have a strong tunability, and it is possible to utilize two-dimensional materials to generate circularly polarized high-order harmonics.…”