Infrared spectra of the CS2−, CS2+, and C2S4+ molecular ions in solid neon and argon

Correlation of the Charge Resonance Interaction with Cluster Conformations Probed by Electronic Spectroscopy of Dimer Radical Cations of CO2 and CS2 in a Cryogenic Ion Trap

Radical cations of dimeric clusters of carbon dioxide/disulfide, [(CX2)2]+• (X = O and S), form strong intracluster bonds through charge resonance (CR) interactions. We herein performed electronic photodissociation spectroscopy of [(CX2)2]+• while regulating the temperature under ambient and cryogenic conditions using a quadrupole ion trap. Both ions exhibited broad band absorption in the near-infrared-visible light region; it is called the "CR band", as a measure of the strength of the CR interaction. Strikingly, this band underwent a noticeable blue shift upon cryogenic cooling for [(CS2)2]+• while not for [(CO2)2]+•. On the basis of quantum chemical calculations with a coupled cluster method, the band shift was attributed to the variations in the relative population of two energetically close conformers found for [(CS2)2]+•. This study highlights a strong correlation between CR interactions and conformation of the radical dimer cations, demonstrating the exceptional significance of cryogenic cooling in the chemistry of ionic molecular clusters.

Identification and Photochemistry of the Mercaptomethyl Radical

The mercaptomethyl radical (·CH2SH) is a higher-energy isomer of the methylthio radical (CH3S·) that has been proposed as an important intermediate in atmospheric and interstellar sulfur chemistry. Herein, we report the spectroscopic identification of ·CH2SH during the UV (365 nm) photolysis of CH3S· in a solid Ar-matrix at 10 K. Upon subsequent irradiation at 266 nm, the dehydrogenation of ·CH2SH to yield CS via the intermediacy of the elusive thioformyl radical (HCS·) has also been observed. The characterization of ·CH2SH and HCS· with matrix-isolation IR and UV-vis spectroscopy is supported by 13C-isotope labeling and quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction theory (VCI). The disclosed photochemistry of ·CH2SH provides new insight into understanding the chemical evolution of organosulfur molecules in the interstellar medium (ISM).

Infrared spectra of HSCS+, c-HSCS, and HCS2− produced on electron bombardment of CS2 in solid para-hydrogen

We report infrared spectra of HSCS⁺, c-HSCS, HCS₂⁻, and other species produced on electron bombardment of a mixture of CS₂ and para-hydrogen during deposition at 3.2 K.

Infrared spectrum of carbon trisulfide in solid argon

Cocondensation of carbon disulfide with high-frequency discharged argon at 4 K produced carbon monosulfide and atomic sulfur, which reacted spontaneously upon annealing to form the carbon trisulfide molecule as identified from the multiplets observed in mixed (12)C, (13)C and (32)S, (34)S isotopic spectra. On the basis of isotopic substitution and theoretical frequency calculations, infrared absorptions at 1263.3 and 570.1 cm(-1) were assigned to predominantly CS stretching and bending vibrations of CS(3) in solid argon. The CS(3) molecule, which was calculated to have a singlet ground state with C(2v) symmetry, dissociated to form the weakly bound SCS-S complex upon visible light irradiation.

Group 4 Transition-Metal Atom Reactions with CS2 and OCS: Infrared Spectra and Density Functional Calculations of SMCS, SM-(η2-CS), SMCO, and OMCS in Solid Argon

Laser-ablated titanium, zirconium, and hafnium atoms were reacted with CS2 and OCS molecules during condensation in excess argon. With CS2, the SMCS and S-M(eta2-CS) products were formed on sample deposition. Photolysis increased both complexes, while annealing favored the lower energy S-M(eta2-CS) side-bound isomer. The OCS reactions produced SMCO, OMCS, and the simple M(eta2-CO)S adduct. Product absorptions are identified by comparison with density functional theory frequency calculations and isotopic substitutions. Investigations with OCS emphasized differences in the CS and CO bond insertion products.

Reactions of Group 3 Transition Metal Atoms with CS2 and OCS: Matrix Isolation Infrared Spectra and Density-Functional Calculations of SMCS, SM-(η2-CS), SMCO, and SM-(η2-CO) in Solid Argon

Laser-ablated scandium, yttrium, and lanthanum atoms were reacted with CS2 and OCS molecules in an argon matrix. Products of the type SMCX and S-M(eta2-CX) (X = S or O) were formed on sample deposition. Photolysis favored the S-M(eta(2)-CX) complex, while annealing increased the more stable SMCX isomer. Product absorptions are identified by density-functional frequency calculations and isotopic substitutions. This work reports the first vibrational spectroscopic characterization of Sc, Y, and La reaction products with CS2 and OCS and the subsequent interconversion between SMCX and S-M(eta2-CX) structural isomers.

The molecular structure and a Renner-Teller analysis of the ground and first excited electronic states of the jet-cooled CS2+ molecular ion

The A 2Pi(u) - X 2Pi(g) electronic band system of the jet-cooled CS2 + ion has been studied by laser-induced fluorescence and wavelength-resolved emission techniques. The ions were produced in a pulsed electric discharge jet using a precursor mixture of carbon disulfide vapor in high-pressure argon. Rotational analysis of the high-resolution spectrum of the 2Pi32 component of the 0(0) 0 band gave linear-molecule molecular structures of r0" = 1.5554(10) A and r0' = 1.6172(12) A. Renner-Teller analyses of the vibronic structure in the spectra showed that the ground-state spin-orbit splitting (A = -447.0 cm(-1)) is much larger than that of the excited state (A = -177.5 cm(-1)), but that the Renner-Teller parameters are of similar magnitude and that a strong nu1 - 2nu2 Fermi resonance occurs in both states. Previous analyses of the vibronic structure in the ground and excited states of the ion from pulsed field-ionization-photoelectron data are shown to be substantially correct.