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As is well-known, the S2 molecule is a ubiquitous intermediate in the combustion, atmosphere, and interstellar space. The six low-lying bound states of S2 have been characterized via photoelectron velocity map imaging and a high-level multi-reference configuration interaction method with the Davidson correction. Spectroscopic constants have been extracted by fitting the potential energy curves extrapolated to the complete basis set limit with a series of Dunning's correlation-consistent basis sets: aug-cc-pV(Q, 5)Z. The calculated spectroscopic parameters well reproduce the experimental results in this work. On the basis of the theoretical calculations, Franck-Condon simulations are performed to assign six adjacent electronic states, especially for three higher overlapping electronic states (c1Σu−, A′3Δu, and A3Σu+). The dissociation energy De of the S2− is evaluated to be 4.111 (4) eV in this work, in agreement with the theoretical prediction (4.056 eV). [ABSTRACT FROM AUTHOR]

L-cysteine S-sulfate, Cys-SSO3H, and their derivatives play essential roles in biological chemistry and pharmaceutical synthesis, yet their intrinsic molecular properties have not been studied to date. In this contribution, the deprotonated anion [cysS-SO3]− was introduced in the gas phase by electrospray and characterized by size-selected, cryogenic, negative ion photoelectron spectroscopy. The electron affinity of the [cysS-SO3]• radical was determined to be 4.95 ± 0.10 eV. In combination with theoretical calculations, it was found that the most stable structure of [cysS-SO3]− (S1) is stabilized via three intramolecular hydrogen bonds (HBs); i.e., one O−H⋯⋯N between the –COOH and –NH2 groups, and two N−H⋯⋯O HBs between –NH2 and –SO3, in which the amino group serves as both HB acceptor and donor. In addition, a nearly iso-energetic conformer (S2) with the formation of an O−H⋯⋯N−H⋯⋯O−S chain-type binding motif competes with S1 in the source. The most reactive site of the molecule susceptible for electrophilic attacks is the linkage S atom. Theoretically predicted infrared spectra indicate that O−H and N−H stretching modes are the fingerprint region (2800 to 3600 cm−1) to distinguish different isomers. The obtained information lays out a foundation to better understand the transformation and structure–reactivity correlation of Cys-SSO3H in biologic settings. [ABSTRACT FROM AUTHOR]

Abstract: A general analytical expression for the calculation of the two-dimensional four-mode Franck–Condon overlap integrals was presented and applied to scrutinize the photoelectron spectroscopy of . Geometry optimization and harmonic vibrational frequency calculations have been performed on the 2B1 state of ClO2 and 1A1 state of by using the density functional theory (B2PLYP functional) and the coupled cluster singles and doubles with perturbative triples [CCSD(T)] methods with various basis sets up to aug-cc-pVQZ. The adiabatic electron affinity of ClO2 was computed by using the CCSD(T) method extrapolated to the complete basis set limit with aug-cc-pVXZ (X=D, T, Q). Franck–Condon analyses and spectral simulation were carried out on the ClO2( 2B1)–( 1A1) photodetachment process. The simulated photoelectron spectrum of are in accord with the experiment. While the Duschinsky effect plays a minor role and can be neglected. In addition, the equilibrium geometry parameters, R(Cl–O)=1.572±0.005Å and (O–Cl–O)=112.5±0.5°, of the 1A1 state of , are obtained by employing an iterative Franck–Condon analysis procedure in the spectral simulations. [ABSTRACT FROM AUTHOR]

On the basis of the harmonic oscillator approximation, the two-dimensional four-mode Franck-Condon vibrational overlap integral under mode-mixing effects has been reduced to a product expression of one-dimensional Gaussian integrals with the aid of expanding Hermite polynomials. A more general analytical expression for the calculation of the two-dimensional four-mode Franck-Condon overlap integrals was derived by directly calculating the Gaussian integrals. This analytical expression was applied to investigate the photoelectron spectra of [image omitted] considering mode-mixing and hot band effects. Geometry optimizations and harmonic vibrational frequency calculations were performed on the [image omitted] 2A1 state of NO2 and the [image omitted] 1A1 state of [image omitted]. Franck-Condon analyses and spectral simulations were carried out on the NO2( [image omitted] 2A1)- [image omitted]( [image omitted] 1A1) photodetachment processes. The spectral simulations of vibrational structures based on the computed Franck-Condon factors are in excellent agreement with the observed spectra. In addition, the equilibrium geometric parameters of the [image omitted] 1A1 state of [image omitted] were obtained in the spectral simulations: bond length R(ON) = 1.248 ± 0.005 Å and bond angle ∠ (ONO) = 116.8 ± 0.5°. [ABSTRACT FROM AUTHOR]

Abstract: A program developed to calculate multidimensional Franck–Condon factors including Duschinsky effects is described and used to simulate the vibrationally resolved photoelectron spectra of S2O− combining with ab initio molecular orbital calculations. Geometry optimizations and harmonic vibrational frequency calculations have been performed on the state of S2O and state of S2O−. Franck–Condon analysis and spectral simulations were carried out on the first photoelectron band of S2O−. The simulated spectra obtained by using B3LYP/6-311+G(3df) are in excellent agreement with the experiment. In addition, the accurate equilibrium geometric parameters, r(ss)=0.1996±0.0005nm and r(so)=0.1514±0.0005nm, of the state of S2O−, are deduced by employing an iterative Franck–Condon analysis procedure in the spectral simulation. Furthermore, the well-resolved theoretical spectrum is derived by improving the resolution of photoelectron spectra in simulations. [Copyright &y& Elsevier]

Background irradiated electrons in photoelectron spectra are known to take place under the ultraviolet light irradiation. Therefore, it deserves discussing the reduction of such electrons in the electron spectra in this work. The main problem present in these electron spectra will largely be overcome through a workflow and process, namely, a combination method of rotating images with angular-tailored and subtracting noise electrons of images which gives rise to non-noise electron peaks. An improved SNR is readily obtained for REMPI-SEVI spectra of 3-bromofluorobenzene (3-Br-FPh) compared with no noise–subtracted and no-angular-tailored spectra. More details are given including electron velocity-map imaging analysis on S − , CuOH − (H 2 O), and 3-Br-FPh in the following sections. [ABSTRACT FROM AUTHOR]

Highlights: [•] We derived an analytical expression to calculate the three-dimensional Franck–Condon integrals. [•] The photoelectron spectrum of was simulated and the role of Duschinsky effects and hot bands were clarified. [•] The equilibrium geometry of was deduced in the spectral simulation. [ABSTRACT FROM AUTHOR]

Abstract: Calculations of Franck–Condon factors are crucial for interpreting vibronic spectra of molecules and studying nonradiative processes. On the base of the closed form expression of the Franck–Condon integrals between arbitrary multidimensional harmonic oscillators under the Duschinsky mixing effects, a more general algebraic expression for the calculation of the three-dimensional four-mode Franck–Condon factors was derived straightforwardly and applied to study the photoelectron spectrum of . Geometry optimization and harmonic vibrational frequency calculations were performed on the state of D2CO at B3LYP, QCISD, CCSD and CASSCF levels, and the state of D2CO+ at CIS, TD-B3LYP, and CASSCF levels. Franck–Condon analyses and spectral simulations were carried out on the photoionization process. The spectral simulations of vibrational structures based on the computed Franck–Condon factors are in excellent agreement with the observed spectrum. In addition, the equilibrium geometric parameters of the state of D2CO+ were obtained in the spectral simulations. [Copyright &y& Elsevier]

Abstract: Geometry optimization and harmonic vibrational frequency calculations were performed on the states of CH3OO/CD3OO and states of CH3OO−/CD3OO− at the B3LYP, QCISD and CCSD levels. The electron affinity energies of CH3OO/CD3OO were calculated at various theory levels. Franck–Condon analyses and spectral simulations were carried out on the photodetachment processes. The spectral simulations of vibrational structures based on the computed Franck–Condon factors are in agreement with the observed spectra. [Copyright &y& Elsevier]