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http://dx.doi.org/10.1103/physrevb.34.5358 | DOI Listing |
J Phys Chem Lett
January 2025
Astronomy Department, University of Maryland, College Park, Maryland 20742, United States.
The CN stretch frequency of neutral, gas-phase 9-cyanoanthracene is 2207 cm (4.531 μm) based on high-resolution infrared absorption experiments coupled with a new hybrid anharmonic quantum chemical methodology. A broad band (full-width at half-maximum of 47 cm) is observed and assigned to multiple transitions, including the CN stretch fundamental and various combination bands that gather intensity from strong anharmonic coupling with the bright CN stretch.
View Article and Find Full Text PDFJ Chem Phys
January 2025
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Two-dimensional (2D) vibrational spectroscopy is a powerful means of investigating the structure and dynamics of complex molecules in condensed phases. However, even in theory, analysis of 2D spectra resulting from complex inter- and intra-molecular motions using only molecular dynamics methods is not easy. This is because molecular motions comprise complex multiple modes and peaks broaden and overlap owing to various relaxation processes and inhomogeneous broadening.
View Article and Find Full Text PDFSpectrochim Acta A Mol Biomol Spectrosc
January 2025
Physics Department, College of Science, King Faisal University, Al Ahsa, 31982, Saudi Arabia. Electronic address:
To consistently determine the anomalous characteristics of phthalic acid crystal (PAC) derivatives, we performed quantum dynamics simulations of the infrared spectral density of the h-PAC and d-PAC isotopomers that show up in the H/D isotopic frequency domain at two different temperatures viz. 77 and 298 K. A theoretical framework explaining the dynamical cooperative interactions within the hydrogen bonds (HBs) in the PAC crystals across a simulation of IR spectral density of the stretching band was developed.
View Article and Find Full Text PDFACS Earth Space Chem
January 2025
School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, U.K.
2-Cyanoindene is one of the few specific aromatic or polycyclic aromatic hydrocarbon (PAH) molecules positively identified in Taurus molecular cloud-1 (TMC-1), a cold, dense molecular cloud that is considered the nearest star-forming region to Earth. We report cryogenic mid-infrared (550-3200 cm) and visible (16,500-20,000 cm, over the ← electronic transition) spectra of 2-cyanoindene radical cations (2CNI), measured using messenger tagging (He and Ne) photodissociation spectroscopy. The infrared spectra reveal the prominence of anharmonic couplings, particularly over the fingerprint region.
View Article and Find Full Text PDFJ Chem Phys
January 2025
Center for Computational Molecular Science and Technology, School of Chemistry and Biochemistry, and School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
We present pyVPT2, a program to perform second-order vibrational perturbation theory (VPT2) computations to obtain anharmonic vibrational frequencies. This program is written in Python and can utilize any of the several quantum chemistry programs that have been interfaced to the QCEngine project of the Molecular Sciences Software Institute (MolSSI). The requisite single point energy, gradient, or Hessian computations can be automatically performed in a distributed-parallel fashion by optionally using the MolSSI's QCFractal software.
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