Measurement of coherent vibrational dynamics with X-ray Transient Absorption Spectroscopy simultaneously at the Carbon K- and Chlorine L- edges.

X-ray Transient Absorption Spectroscopy (XTAS) is a powerful probe for ultrafast molecular dynamics. The evolution of XTAS signal is controlled by the shapes of potential energy surfaces of the associated core-excited states, which are difficult to directly measure. Here, we study the vibrational dynamics of Raman activated CCl with XTAS targeting the C 1s and Cl 2p electrons.

Differentiating multi-MeV, multi-ion spectra with CR-39 solid-state nuclear track detectors.

The development of high intensity petawatt lasers has created new possibilities for ion acceleration and nuclear fusion using solid targets. In such laser-matter interaction, multiple ion species are accelerated with broad spectra up to hundreds of MeV. To measure ion yields and for species identification, CR-39 solid-state nuclear track detectors are frequently used.

Signatures of the Bromine Atom and Open-Shell Spin Coupling in the X-ray Spectrum of the Bromobenzene Cation.

Tabletop X-ray spectroscopy measurements at the carbon -edge complemented by calculations are used to investigate the influence of the bromine atom on the carbon core-valence transitions in the bromobenzene cation (BrBz). The electronic ground state of the cation is prepared by resonance-enhanced two-photon ionization of neutral bromobenzene (BrBz) and probed by X-rays produced by high-harmonic generation (HHG). Replacing one of the hydrogen atoms in benzene with a bromine atom shifts the transition from the 1s orbital of the carbon atom (C*) bonded to bromine by ∼1 eV to higher energy in the X-ray spectrum compared to the other carbon atoms (C).

Ultrafast X-ray Spectroscopy of Intersystem Crossing in Hexafluoroacetylacetone: Chromophore Photophysics and Spectral Changes in the Face of Electron-Withdrawing Groups.

Intersystem crossings between singlet and triplet states represent a crucial relaxation pathway in photochemical processes. Herein, we probe the intersystem crossing in hexafluoro-acetylacetone with ultrafast X-ray transient absorption spectroscopy at the carbon K-edge. We observe the excited state dynamics following excitation with 266 nm UV light to the ππ* (S) state with element and site-specificity using a broadband soft X-ray pulse produced by high harmonic generation.

Correction: Jahn-Teller distortion and dissociation of CCl by transient X-ray spectroscopy simultaneously at the carbon K- and chlorine L-edge.

[This corrects the article DOI: 10.1039/D2SC02402K.].

Jahn-Teller distortion and dissociation of CCl by transient X-ray spectroscopy simultaneously at the carbon K- and chlorine L-edge.

X-ray Transient Absorption Spectroscopy (XTAS) and theoretical calculations are used to study CCl prepared by 800 nm strong-field ionization. XTAS simultaneously probes atoms at the carbon K-edge (280-300 eV) and chlorine L-edge (195-220 eV). Comparison of experiment to X-ray spectra computed by orbital-optimized density functional theory (OO-DFT) indicates that after ionization, CCl undergoes symmetry breaking driven by Jahn-Teller distortion away from the initial tetrahedral structure (T) in 6 ± 2 fs.

X-ray transient absorption reveals the A (nπ*) state of pyrazine in electronic relaxation.

Electronic relaxation in organic chromophores often proceeds via states not directly accessible by photoexcitation. We report on the photoinduced dynamics of pyrazine that involves such states, excited by a 267 nm laser and probed with X-ray transient absorption spectroscopy in a table-top setup. In addition to the previously characterized B (ππ*) (S) and B (nπ*) (S) states, the participation of the optically dark A (nπ*) state is assigned by a combination of experimental X-ray core-to-valence spectroscopy, electronic structure calculations, nonadiabatic dynamics simulations, and X-ray spectral computations.

Structural Insights from Tandem Mass Spectrometry, Ion Mobility-Mass Spectrometry, and Infrared/Ultraviolet Spectroscopy on Sphingonodin I: Lasso vs Branched-Cyclic Topoisomers.

Lasso peptides form a class of ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by a mechanically interlocked topology, where the C-terminal tail of the peptide is threaded and trapped within an N-terminal macrolactam ring. Sphingonodin I is a lasso peptide that has not yet been structurally characterized using the traditional structural biology tools (e.g.

Table-Top X-ray Spectroscopy of Benzene Radical Cation.

Ultrafast table-top X-ray spectroscopy at the carbon K-edge is used to measure the X-ray spectral features of benzene radical cations (Bz). The ground state of the cation is prepared selectively by two-photon ionization of neutral benzene, and the X-ray spectra are probed at early times after the ionization by transient absorption using X-rays produced by high harmonic generation (HHG). Bz is well-known to undergo Jahn-Teller distortion, leading to a lower symmetry and splitting of the π orbitals.

Interplay of Open-Shell Spin-Coupling and Jahn-Teller Distortion in Benzene Radical Cation Probed by X-ray Spectroscopy.

We report a theoretical investigation and elucidation of the X-ray absorption spectra of neutral benzene and of the benzene cation. The generation of the cation by multiphoton ultraviolet (UV) ionization and the measurement of the carbon K-edge spectra of both species using a table-top high-harmonic generation source are described in the companion experimental paper [Epshtein, M.; et al.

Separation and Identification of Glycan Anomers Using Ultrahigh-Resolution Ion-Mobility Spectrometry and Cryogenic Ion Spectroscopy.

The analysis of carbohydrates, or glycans, is challenging for established structure-sensitive gas-phase methods. The multitude of possible stereo-, regio-, and structural isomers makes them substantially more complex to analyze than DNA or proteins, and no one method is currently able to fully resolve them. While the combination of tandem mass spectrometry (MS) and ion-mobility spectrometry (IMS) have made important inroads in glycan analysis, in many cases, this approach is still not able to identify the precise isomeric form.

Cryogenic Ion Spectroscopy for Identification of Monosaccharide Anomers.

We combine conformer-selective, cryogenic infrared spectroscopy, quantum mechanical computations, and O substitution at the reducing end to determine the structural preferences of protonated glucosamine in the gas phase. Cryogenic infrared-infrared (IR-IR) double resonance spectroscopy of helium-tagged, protonated glucosamine provides vibrational fingerprints of individual conformers, and O isotopic labeling facilitates the match with computed structures and provides a selective probe of the anomeric hydroxyl. This is key for using vibrational spectroscopy for glycan analysis and determining the generality of anomeric memory during glycosidic bond cleavage.

Infrared Spectroscopy as a Probe of Electronic Energy Transfer.

We have combined electronic and vibrational spectroscopy in a cryogenic ion trap to produce highly resolved, conformer-selective spectra for the ground and excited states of a peptide containing two chromophores. These spectra permit us to determine the precise three-dimensional structure of the peptide and give insight into the migration of the electronic excitation from phenylalanine to tyrosine because changes in the excited-state infrared spectra are sensitive to localization of the electronic energy in each chromophore. The well-controlled experimental conditions make this result a stringent test for theoretical methods dealing with electronic energy transfer.

The Structure of the Protonated Serine Octamer.

The amino acid serine has long been known to form a protonated "magic-number" cluster containing eight monomer units that shows an unusually high abundance in mass spectra and has a remarkable homochiral preference. Despite many experimental and theoretical studies, there is no consensus on a SerH structure that is in agreement with all experimental observations. Here, we present the structure of SerH determined by a combination of infrared spectroscopy and ab initio molecular dynamics simulations.

Can Mutational Analysis Be Used To Assist Structure Determination of Peptides?

Mutational analysis is widely used to study the relationship between sequence and structure of proteins and peptides. It is often assumed that substituting a proline with another amino acid "locks" the peptide bond in the trans conformation, allowing only a subset of the initial molecular geometries to be observed. To test this assumption, we assess the result of substituting two prolines in the bradykinin sequence with alanine using field-asymmetric ion mobility spectrometry combined with cryogenic ion spectroscopy in the gas phase.