Vapor Phase Infrared Spectroscopy and Ab Initio Fundamental Anharmonic Frequencies of Ammonia Borane

Journal Article · Thu Mar 29 04:00:00 EDT 2012 · Journal of Physical Chemistry A, 116(12):3124-3136

DOI:https://doi.org/10.1021/jp2115753· OSTI ID:1038366

Sams, R L; Xantheas, Sotiris S; Blake, Thomas A

Infrared absorption spectra of ammonia borane vapor have been recorded between 3600 and 600 cm-1. Of the eleven infrared active modes, seven of the vibrational modes of NH3 11BH3 have been observed and four of the vibrational modes of NH3 10BH3 were observed. The spectra were recorded with sufficient resolution to observe the rotational structure of the bands, which allowed for preliminary least squares fitting of the band origins and rotational constants. First principals electronic structure calculations were performed to obtain anharmonic band origins and their intensities. The band assignments are discussed in relation to other spectroscopic techniques that have been used to study this molecule. A semi empirical estimate of the vapor pressure of ammonia borane at room temperature (22 °C) was made and found to be ~ 1 × 10-4 Torr. The assignment of the measured modes was aided by the calculated anharmonic frequencies and their infrared intensities. The combination of the CCSD(T) harmonic frequencies with the B3LYP anharmonicities, obtained from second order vibrational perturbation theory, was found to produce an overall best agreement with the measured band origins.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1038366
• Report Number(s): PNNL-SA-84352; 43893; KC0301020
• Journal Information: Journal of Physical Chemistry A, 116(12):3124-3136, Journal Name: Journal of Physical Chemistry A, 116(12):3124-3136 Journal Issue: 12 Vol. 116; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
AMMONIA
Ammonia borane
BORANES
ELECTRONIC STRUCTURE
Environmental Molecular Sciences Laboratory
HARMONICS
PERTURBATION THEORY
RESOLUTION
SPECTRA
SPECTROSCOPY
VAPOR PRESSURE
ab initio
anharmonic vibrational modes
quantum chemistry
infrared spectroscopy