High-resolution Fourier transform infrared spectroscopy of high-temperature molecules and free radicals.

Abstract

High resolution absorption spectra of the IF molecule in the X¹Σ⁺ ground state were observed with the Kitt Peak Fourier transform spectrometer in a F₂/I₂ flame. Iodine fluoride is the most unstable interhalogen compound. Accurate wavenumber measurements (±0.0002 cm⁻¹) were made for the 1-0, 2-1 and 2-0 bands and molecular constants were derived. The observation of a high resolution emission spectrum at 13 μm (750 cm⁻¹) is unusual. Seven bands (1-0 through 7-6) of the main isotopic form, ²⁸Si³²S, were observed along with three bands (1-0, 2-1 and 3-2) for each of the minor species, ²⁹Si³²S, ³⁰Si³²S and ²⁸Si³⁴S. More than 2450 lines were fitted for this important astrophysical molecule. Dunham coefficients were obtained for each isotopomer of SiS. Mass-reduced Dunham parameters, including Watson's correction due to the breakdown of the Born-Oppenheimer approximation, were also derived from the data. The first high resolution spectrum of a metal dihalides was recorded by infrared emission spectroscopy. The infrared emission spectrum of BeF₂ was observed in the region of the antisymmetric stretching mode, ν₃, and the combination band, ν₁ + ν₂. Eight vibration-rotation bands were rotationally analyzed and the spectroscopic constants are reported. The equilibrium beryllium fluoride bond distance (rₑ) was found to be 1.3729710(95)Å in BeF₂. Values of the vibrational frequencies of all the three normal modes were obtained from the spectra. The gas phase infrared spectrum of C₆₀ (buckminsterfullerine) has been observed in emission with the National Solar Observatory Fourier transform spectrometer at Kitt Peak. Bands attributable to the C₆₀ molecule are found at 527.1 cm⁻¹, 570.3 cm⁻¹, 1169.1 cm⁻¹ and 1406.9 cm⁻¹. Additional emission features are tentatively assigned to C₇₀ or combination bands of C₆₀. A new, strong emission is observed at 1010.2 cm⁻¹ belonging to an unknown molecule. A new electronic state of ³Π symmetry of PtO has been observed between 7100 cm⁻¹ and 8015 cm⁻¹ above the ground state. This new state was observed through an electronic transition to the ³Σ⁻ ground state of this free radical. Three independent electronic systems connecting the Ω = 0,1 and 2 spin components in the upper state to Ω = 1 component in the ground state have been recorded in emission with the Fourier transform spectrometer associated with the McMath Solar Telescope at Kitt Peak. (Abstract shortened with permission of author.)