State-selective dissociative double ionization of CH3I and CH2I2 via I 4d core-hole states studied by multi-electron-ion coincidence spectroscopy.

The dissociative double ionization of CH3I and CH2I2 irradiated with extreme ultraviolet light at hv = 100 eV is investigated by multi-electron-ion coincidence spectroscopy using a magnetic bottle type electron spectrometer. The spin-orbit state-resolved Auger electron spectra for the I 4d core-hole states, (I 4d3/2)-1 and (I 4d5/2)-1, provide clear identifications of electronic states of CH3I2+ and CH2I22+. The dominant ion species produced after the double ionization correlate with the Auger electron energy, showing that different fragmentation pathways are open depending on the electronic states populated by the Auger decay.

Exploring the ultrafast and isomer-dependent photodissociation of iodothiophenes site-selective ionization.

C-I bond extension and fission following ultraviolet (UV, 262 nm) photoexcitation of 2- and 3-iodothiophene is studied using ultrafast time-resolved extreme ultraviolet (XUV) ionization in conjunction with velocity map ion imaging. The photoexcited molecules and eventual I atom products are probed by site-selective ionization at the I 4d edge using intense XUV pulses, which induce multiple charges initially localized to the iodine atom. At C-I separations below the critical distance for charge transfer (CT), charge can redistribute around the molecule leading to Coulomb explosion and charged fragments with high kinetic energy.

Dissociation following the Auger decay of xenon difluoride molecules.

This study investigated the dissociation after the Xe 4d Auger decay of weak-bonding XeF2 molecules by multielectron-ion coincidence spectroscopy using a magnetic bottle electron spectrometer. Fragmentations from the XeF22+ states were clarified in the Auger spectra coincident with individual ion species. It was observed that the two-hole population led by the Auger decay was not directly inherited during the fragmentation of XeF22+.

Metastability and fragmentation of the OCS3+ states produced by S 2p double Auger decay.

The metastability and the dissociation processes of the OCS3+ states produced by the S 2p double Auger decay of OCS are investigated by multi-electron-ion coincidence spectroscopy using a magnetic bottle electron spectrometer. The spectra of the OCS3+ states filtered for the production of individual ions are derived by four-fold (or five-fold) coincidence among three electrons and a product ion (or two ions). The ground OCS3+ state is confirmed to be metastable in the 10 µs regime.

Coster-Kronig and super Coster-Kronig transitions from the Xe 4s core-hole state.

Coster-Kronig and super Coster-Kronig transitions from the Xe 4s core-hole state are investigated by coincidence detection of all the emitted electrons and product ions. The branching ratios of the transitions are determined by analyzing the coincidence data and comparing them to calculations. Subsequent decay pathways following these first-step Auger decays are also clarified.

Specific chemical bond relaxation unraveled by analysis of shake-up satellites in the oxygen single site double core hole spectrum of CO.

We recently developed [A. Ferté, , , 2020, , 4359] a method to compute single site double core hole (ssDCH or K) spectra. We refer to that method as NOTA+CIPSI.

Characterization of soft X-ray FEL pulse duration with two-color photoelectron spectroscopy.

The pulse duration of soft X-ray free-electron laser (FEL) pulses of SACLA BL1 (0.2-0.3 nC per bunch, 0.

Advanced Computation Method for Double Core Hole Spectra: Insight into the Nature of Intense Shake-up Satellites.

Double core hole spectroscopy is an ideal framework for investigating photoionization shake-up satellites. Their important intensity in a single site double core hole (ssDCH) spectrum allows the exploration of the subtle mix of relaxation and correlation effects associated with the inherent multielectronic character of the shake-up process. We present a high-accuracy computation method for single photon double core-shell photoelectron spectra that combines a selected configuration interaction procedure with the use of non-orthogonal molecular orbitals to obtain unbiased binding energy and intensity.

Zeeman quantum beats of helium Rydberg states excited by synchrotron radiation.

Quantum beats in fluorescence decay from Zeeman-split magnetic sublevels have been measured for helium Rydberg states excited by synchrotron radiation. The Zeeman quantum beats observed in this prototypical case were fitted with an equation from a theoretical formulation. It is proposed that Zeeman quantum beat measurement can be a useful way to simply evaluate the polarization characteristics of extreme ultraviolet light.

Multiple Auger decays of core-excited states in N.

Multi-electron coincidence measurements have been performed at the photon energies for the core-to-valence (1s → π) and core-to-Rydberg (1s → 3sσ and 3pπ) resonant excitations in N in order to investigate the dynamics of multiple Auger-electron emissions from these core-excited states in detail. Peaks due to slow electrons from superexcited atomic fragments are observed in the decay processes by emission of two or three Auger electrons, indicating stepwise (cascade) multiple Auger decays that involve faster dissociations than electronic relaxations. Energy partitions between the emitted electrons enable us to reveal the detailed decay mechanisms for these processes.

A virtual stretch of light pulse interval by pulsed electron extraction introduced into a magnetic bottle electron spectrometer.

A pulsed extraction of electrons associated with a single light pulse is introduced into electron time-of-flight measurement by using a magnetic bottle electron spectrometer. The pulsed extraction enables us to observe long times-of-flight of electrons with synchrotron radiation pulses of short periods. The feasibility and the performance of this method are demonstrated by multielectron coincidence measurements for Xe 4d excitation/ionization.

Observation of an optical vortex beam from a helical undulator in the XUV region.

The observation of an optical vortex beam at 60 nm wavelength, produced as the second-harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam.

Site-Specific Electron-Relaxation Caused by Si:2p Core-Level Photoionization: Comparison between FSiCHCHSi(CH) and ClSiCHCHSi(CH) Vapors by Means of Photoelectron Auger Electron Coincidence Spectroscopy.

Site-specific electron relaxations caused by Si:2p core-level photoionizations in FSiCHCHSi(CH) and ClSiCHCHSi(CH) vapors have been studied by means of the photoelectron Auger electron coincidence spectroscopy. FSiCHCHSi(CH) shows almost 100% site-specificity in fragmentation caused by the Si:2p ionization. However, substitution of Cl for F of FSiCHCHSi(CH) considerably reduces the site-specificity at the Si atom bonded to three halogen atoms, with the site-specificity at the Si site bonded to three methyl groups remaining largely unchanged.

Detection of Neutral Species in the MALDI Plume Using Femtosecond Laser Ionization: Quantitative Analysis of MALDI-MS Signals Based on a Semiequilibrium Proton Transfer Model.

We investigated neutral species in the matrix-assisted laser desorption and ionization (MALDI) plume using femtosecond laser ionization spectrometry with simultaneous measurement of the standard MALDI spectrum of the identical MALDI event induced by pulsed UV laser irradiation. The ratio of neutral species in the plume [A]/[M] (A = phenylalanine (Phe) or alanine (Ala), M = 2,5-dihydroxybenzoic acid (DHB)) was confirmed to be the same as that of the sample mixture in the range of [A]/[M] = 4 × 10-1, indicating the validity of the widely adopted approximation [A]/[M] = [A]/[M] in the reaction quotient of the proton transfer reaction MH + A ⇄ M + AH. An effective parameter representing the extent of thermal equilibrium in the thermal proton transfer model is introduced for the first time.

Auger decay of molecular double core-hole and its satellite states: comparison of experiment and calculation.

Auger decay of the C(2)H(2) double core-hole (DCH) states, including the single-site DCH (C1s(-2)), two-site DCH (C1s(-1)C1s(-1)), and satellite (C1s(-2)π(-1)π∗(+1)) states, has been investigated experimentally using synchrotron radiation combined with multi-electron coincidence method, and theoretically with the assumption of the two-step sequential model for Auger decay of the DCH states. The theoretical calculations can reproduce the experimental two-dimensional Auger spectra of the C(2)H(2) single-site DCH and satellite decays, and allow to assign the peaks appearing in the spectra in terms of sequential two-electron vacancy creations in the occupied valence orbitals. In case of the one-dimensional Auger spectrum of the C(2)H(2) two-site DCH decay, the experimental and calculated results agree well, but assignment of peaks is difficult because the first and second Auger components overlap each other.

Angle-resolved metastable fragment yields spectra of N2 and CO in K-edge excitation energy region.

Angle-resolved metastable fragments yields spectra have been measured in the N 1s ionization region of the N(2) and C 1s ionization region of CO. These spectra are compared with zero kinetic energy electron and photoelectron spectra. It has been shown that an isotropic metastable fragments yields spectra are almost identical with the ZEKE spectrum, whereas metastable fragments yields spectra with the Σ-Σ transition show similarity with photoelectron spectra.

A magnetic-bottle multi-electron-ion coincidence spectrometer.

A novel multi-electron-ion coincidence spectrometer developed on the basis of a 1.5 m-long magnetic-bottle electron spectrometer is presented. Electrons are guided by an inhomogeneous magnetic field to a detector at the end of the flight tube, while a set of optics is used to extract counterpart ions to the same detector, by a pulsed inhomogeneous electric field.

Multi-electron spectroscopy: Auger decays of the argon 2s hole.

Auger decay of an inner shell hole is an efficient way to create multiply charged ions in the gas phase. We illustrate this with the example of the argon 2s decay, and show that multi-electron coincidence spectroscopy between the 2s photoelectron and all released Auger electrons leads to a complete reconstruction of the Ar 2s decay cascade. Spectra of the intermediate and final Ar(n+) states are obtained and are compared with a theoretical model.

Application of a simple asynchronous mechanical light chopper to multielectron coincidence spectroscopy.

A simple asynchronous mechanical light chopper, based on modification of a turbo-molecular pump, has been developed to extend the interval between light pulses in single bunch operation at the Photon Factory storage ring. A pulse repetition rate of 80 kHz was achieved using a cylinder rotating at 48000 rpm, with 100 slits of 80 microm width. This allows absolute timing of particles up to 12.

Inner-valence states of N2+ and the dissociation dynamics studied by threshold photoelectron spectroscopy and configuration interaction calculation.

The N2(+) states lying in the ionization region of 26-45 eV and the dissociation dynamics are investigated by high-resolution threshold photoelectron spectroscopy and threshold photoelectron-photoion coincidence spectroscopy. The threshold photoelectron spectrum exhibits several broad bands as well as sharp peaks. The band features are assigned to the N2(+) states associated with the removal of an inner-valence electron, by a comparison with a configuration interaction calculation.

Autoionization and neutral dissociation of superexcited HI studied by two-dimensional photoelectron spectroscopy.

Two-dimensional photoelectron spectroscopy of hydrogen iodide (HI) has been performed in the photon energy region of 11.10-14.85 eV, in order to investigate dynamical properties on autoionization and neutral dissociation of Rydberg states HI*(RA) converging to HI+(A 2Sigma1/2(+)).