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Attosecond Streaking Time Delays: Finite-Range Interpretation and Applications
摘要： We review theoretical studies of the attosecond streaking time delay concept in photoionization via the investigation of the electron dynamics in the streaking field after the transition of the photoelectron into the continuum upon absorption of an extreme ultraviolet photon. Based on the results, a so-called finite range interpretation was introduced, which highlighted that the delay is accumulated until the streaking pulse ends and, hence, over a finite range of the potential of the parent ion. Following a discussion of the analysis leading to this interpretation, we summarize a few applications which provide insights into different aspects of the streaking time delay concept in photoionization. Besides a review of previously presented results, we give an analysis of the relevance of the first half-cycle of the streaking field and an outlook regarding the perspective of using the streaking method to resolve dynamical changes in the potential that the photoelectron explores during its propagation in the continuum.
关键词： attosecond measurement techniques,streaking time delays,photoionization,ultrafast laser science
更新于2025-09-19 17:15:36
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Electron correlation effects in the photoionization of CO and isoelectronic diatomic molecules
摘要： This paper investigates the first sigma satellite band, which is by far the most prominent, in the valence photoelectron spectra for a set of isoelectronic diatomic molecules: carbon monoxide, carbon monosulfide, carbon monoselenide, silicon monoxide and boron monofluoride. In particular, we analyze the effect of the electronic structure, with the change of the atomic pair along the row and column of the periodic table on the position of the satellite peak as well as on the related dynamical observables profiles. For this investigation, highly correlated calculations have been performed on the primary ionic states and the satellite band for all the molecules considered. Cross sections for the primary ionic states, calculated using Dyson orbitals, have been compared with those obtained with Hartree–Fock and Density Functional Theory to probe the impact of the correlation in the bound states on the photoionization observables. Limitations of a simple intensity borrowing mechanism clearly result from the analysis of the satellite state, characterized by different features with respect to the relevant primary states.
关键词： isoelectronic molecules,photoelectron spectra,photoionization,electron correlation,Dyson orbitals
更新于2025-09-19 17:15:36
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Time domain study on the tunneling dynamics in photoionization microscopy
摘要： The time-dependent wave-packet theory is used to study the tunneling dynamics during the photoionization microscopy in the time domain. The results show both the ionized electron current in the time domain and the radial distribution in the spatial domain originate from two contributions: the quantum tunneling ionization of quasi-bound states and the classical above-barrier ionization of continuous states. The two types of ionization exhibit different temporal characters, resulting in the spatial probability distribution depends on the detection time. For atoms in parallel electric and magnetic fields, the interference narrowing effect is confirmed from the two aspects: the line width evolution and electron current distribution. Tunneling ionization reaches its maximum at the point of levels anti-crossing. This makes it possible to observe node structures in photoionization microscopy of atom or molecule with strong states mixing.
关键词： photoionization microscopy,numerical simulation,tunneling effect
更新于2025-09-19 17:15:36
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Few-cycle laser driven reaction nanoscopy on aerosolized silica nanoparticles
摘要： Nanoparticles offer unique properties as photocatalysts with large surface areas. Under irradiation with light, the associated near-fields can induce, enhance, and control molecular adsorbate reactions on the nanoscale. So far, however, there is no simple method available to spatially resolve the near-field induced reaction yield on the surface of nanoparticles. Here we close this gap by introducing reaction nanoscopy based on three-dimensional momentum-resolved photoionization. The technique is demonstrated for the spatially selective proton generation in few-cycle laser-induced dissociative ionization of ethanol and water on SiO2 nanoparticles, resolving a pronounced variation across the particle surface. The results are modeled and reproduced qualitatively by electrostatic and quasi-classical mean-field Mie Monte-Carlo (M3C) calculations. Reaction nanoscopy is suited for a wide range of isolated nanosystems and can provide spatially resolved ultrafast reaction dynamics on nanoparticles, clusters, and droplets.
关键词： ethanol,water,SiO2 nanoparticles,photocatalysts,nanoparticles,Mie Monte-Carlo calculations,momentum-resolved photoionization,reaction nanoscopy,near-fields
更新于2025-09-19 17:13:59
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Binding energies and photoionization cross-sections of donor impurities in GaN/AlxGa1a??xN spherical quantum dot under hydrostatic pressure
摘要： In this paper, the binding energy and photoionization cross-section of donor impurity state in GaN/AlxGa1?xN quantum dot structure are studied theoretically by using variational method. The variation of binding energy and photoionization cross-section with core and shell sizes at di?erent impurity locations under hydrostatic pressure is calculated numerically. The results show that the binding energy decreases monotonously with the core size at di?erent impurity locations for GaN/AlxGa1?xN core/shell quantum dot. In contrast, for the inverted core/shell quantum dot, the binding energy exhibits di?erent trends with the increase of core size at di?erent impurity locations. But the binding energy decreases monotonically with the shell size for both of them. Moreover, when the photon energy is approximately equal to the donor binding energy, the peak of the photoionization cross-section appears. There will be di?erent peak shifts under di?erent conditions, and its peak intensity increases with the increase of core and shell sizes. When the hydrostatic pressure is applied, the binding energy and the peak strength of the photoionization cross-section increase with the increase of the pressure.
关键词： hydrostatic pressure,Spherical quantum dot,binding energy,photoionization cross-section
更新于2025-09-19 17:13:59
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Highly selective and sensitive online measurement of trace exhaled HCN by acetone-assisted negative photoionization time-of-flight mass spectrometry with in-source CID
摘要： Exhaled hydrogen cyanide (HCN) has been extensively investigated as a promising biomarker of the presence of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) disease. Its concentration profile for exhalation can provide useful information for medical disease diagnosis and therapeutic procedures. However, the complexity of breath gas, like high humidity, carbon dioxide (CO2) and trace organic compounds, usually leads to quantitative error, poor selectivity and sensitivity for HCN with some of existing analytical techniques. In this work, acetone-assisted negative photoionization (AANP) based on a vacuum ultraviolet (VUV) lamp with a time-of-flight mass spectrometer (AANP-TOFMS) was firstly proposed for online measurement of trace HCN in human breath. In-source collision-induced dissociation (CID) was adopted for sensitivity improvement and the signal response of the characteristic ion CN? (m/z 26) was improved by about 24-fold. For accurate and reliable analysis of the exhaled HCN, matrix influences in the human breath including humidity and CO2 were investigated, respectively. A Nafion tube was used for online dehumidification of breath samples. Matrix-adapted calibration in the concentration range of 0.5–50 ppbv with satisfactory dynamic linearity and repeatability was obtained. The limit of quantitation (LOQ) for HCN at 0.5 ppbv was achieved in the presence of 100% relative humidity and 4% CO2. Finally, the method was successfully applied for online determination of human mouth- and nose-exhaled HCN, and the nose-exhaled HCN were proved to be reliable for assessing systemic HCN levels for individuals. The results are encouraging and highlight the potential of AANP-TOFMS with in-source CID as a selective, accurate, sensitive and noninvasive technique for determination of the exhaled HCN for CF clinical diagnosis and HCN poisoning assessment.
关键词： Cystic fibrosis,Acetone-assisted negative photoionization,Hydrogen cyanide,Time-of-flight mass spectrometry,Pseudomonas aeruginosa,In-source collision-induced dissociation
更新于2025-09-19 17:13:59
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Lanczos-based equation-of-motion coupled-cluster singles-and-doubles approach to the total photoionization cross section of valence excited states
摘要： Excitation energies and oscillator strengths of the first two electronically excited states of helium, water, sulfur dioxide, molecular nitrogen, and carbon monoxide were obtained from an asymmetric-Lanczos-based formulation of the equation-of-motion coupled cluster singles and doubles approach. The total photoionization cross sections were generated by two different methodologies: an analytic continuation procedure based on the Padé approximants and the Stieltjes imaging technique. The results are compared with theoretical photoionization cross sections from algebraic diagrammatic construction [ADC(2)] and ADC(2)-x calculations [M. Ruberti et al., J. Chem. Phys. 140, 184107 (2014)] and with available experimental data.
关键词： Stieltjes imaging technique,coupled-cluster singles-and-doubles,photoionization cross section,Lanczos-based equation-of-motion,valence excited states,Padé approximants
更新于2025-09-12 10:27:22
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THz Generation from Relativistic Plasmas Driven by Near- to Far-Infrared Laser Pulses
摘要： Terahertz pulse generation by ultraintense two-color laser fields ionizing gases with near- to far-infrared carrier wavelength is studied from particle-in-cell simulations. For a long pump wavelength (10.6 μm) promoting a large ratio of electron density over critical, photoionization is shown to catastrophically enhance the plasma wakefield, causing a net downshift in the optical spectrum and exciting THz fields with tens of GV/m amplitude in the laser direction. This emission is accompanied by coherent transition radiation (CTR) of comparable amplitude due to wakefield-driven electron acceleration. We analytically evaluate the fraction of CTR energy up to 30% of the total radiated emission including the particle self-field and numerically calibrate the efficiency of the matched blowout regime for electron densities varied over three orders of magnitude.
关键词： photoionization,laser-plasma interaction,plasma wakefield,Terahertz,coherent transition radiation,particle-in-cell simulations
更新于2025-09-12 10:27:22
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High-Resolution Threshold Photoelectron Spectroscopy by Vacuum Ultraviolet Laser Velocity-Map-Imaging Method
摘要： We have obtained the high-resolution threshold photoelectron (TPE) spectra of chlorobenzene C6H5Cl (X 1A1), propargyl radical C3H3 (X 2B1), and allyl radical C3H5 (X 2A1) by employing the vacuum ultraviolet (VUV) laser velocity-map-imaging-TPE (VUV-VMI-TPE) method. The photoelectron energy resolution of 1(cid:0)2 cm?1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron (VUV-PFI-PE) measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron (VUV-VMI-PE) and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements F in cm?1, which is half of the classical prediction of F in cm?1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7 (n=0(cid:0)3), for C3H+ 5 . The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI-TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.
关键词： Velocity-map imaging,Photoionization,Threshold photoelectron,Radical
更新于2025-09-11 14:15:04
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Pump-Probe Study of Plasma Dynamics in Gas-Filled Photonic Crystal Fiber Using Counterpropagating Solitons
摘要： We present a pump-probe technique for monitoring ultrafast polarizability changes. In particular, we use it to measure the plasma density created at the temporal focus of a self-compressing higher-order pump soliton in a gas-?lled hollow-core photonic crystal ?ber. This is done by monitoring the wavelength of the dispersive wave emission from a counterpropagating probe soliton. By varying the relative delay between pump and probe, the plasma density distribution along the ?ber can be mapped out. Compared with recently introduced interferometric side probing for monitoring the plasma density, our technique is relatively immune to instabilities caused by air turbulence and mechanical vibration. The results of two experiments on argon- and krypton-?lled ?ber are presented and compared to numerical simulations. The technique provides an important tool for probing photoionization in many di?erent gases and gas mixtures, as well as ultrafast changes in dispersion in many other contexts.
关键词： photoionization,solitons,plasma density,photonic crystal fiber,pump-probe technique
更新于2025-09-11 14:15:04