Analysis of the A∼-X∼ bands of the ethynyl radical near 1.48

Anh Le¹,

Eisen C. Gross²,

Gregory E. Hall³

et al.

Abstract

We report the observation and analysis of spectra in part of the near-infrared spectrum of C 2 H, originating in rotational levels in the ground and lowest two excited bending vibrational levels of the groundX 2 Σ + state. In the analysis, we have combined present and previously reported high resolution spectroscopic data for the lower levels involved in the transitions to determine significantly improved molecular constants to describe the fine and hyperfine split rotational levels of the radical in the zero point, v 2 = 1 and the 2 Σ + component of v 2 = 2. Two of the upper state vibronic levels involved had not been observed previously. The data and analysis indicate the electronic wavefunction character changes with bending vibrational excitation in the ground state and provide avenues for future measurements of reactivity of the radical as a function of vibrational excitation.

The 1.66 $μ$m Spectrum of the Ethynyl Radical, CCH

“…The data were recorded several years ago at Brookhaven National Laboratory, and the frequency-modulated laser transient absorption spectrometer used has been described in detail previously. [14,13,15,16,17] The radicals were formed by a 193 nm ArF excimer laser photolysis of a sample of (1,1,1)trifluoro propyne, CF 3 CCH. Premixed samples containing 10 % of precursor diluted in argon were prepared and the mixture flowed slowly through the absorption cell at a constant pressure of 500 mtorr.…”

“…The active pathlength was several meters. [13,14] The ArF photolysis laser firing pulse was used to trigger the digital oscilloscope used to acquire the data. A Bristol Instruments model 621B wavemeter was used to measure the diode laser wavenumber.…”

Kinetic study of the OH + ethylene reaction using frequency‐modulated laser absorption spectroscopy

“…The OH radical kinetics reported here were measured inside a Herriott‐type slow flow reactor using FM laser absorption spectroscopy. This technique and apparatus have been described in detail elsewhere . Briefly, gas flows of nitric acid (HNO 3 ), C 2 H 4 and argon were regulated using calibrated mass flow controllers and flowed into a 2‐m glass Herriott‐type flow tube.…”

“…This technique and apparatus have been described in detail elsewhere. 43,[50][51][52]55,56 Briefly, gas flows of nitric acid (HNO 3 ), C 2 H 4 and argon were regulated using calibrated mass flow controllers and flowed into a 2-m glass Herriott-type flow tube. The total pressure inside the flow tube was controlled by adjusting a throttling valve on the exhaust line to a liquid nitrogen-trapped rotary pump (Pfeiffer, PK D56 112), and measured using capacitance manometers (MKS, 622c; Edwards, 600 AB).…”

“…FM spectroscopy offers several advantages as a detection method for kinetics studies of small reactive intermediates such as CN, NH 2 , CH 2 , HCO, and more recently, HO 2 , C 2 H, and OH . Compared to more commonly applied laser‐induced fluorescence methods for the investigation of OH reactions, the absorption‐based FM methods have a simpler dependence of the sensitivity on pressure and temperature conditions.…”