The Ã 2Π–X̃ 2Σ+ transition of HC2 isolated in solid argon

Abstract

Fourier transform absorption spectra have been obtained between 700 and 7900 cm−1 at a resolution of 0.2 cm−1 for Ar:C2H2 samples codeposited at 12 K with a beam of argon atoms that had been excited in a microwave discharge. Detailed isotopic substitution studies have confirmed that the predominant product species is HC2, which contributes not only the absorptions previously assigned to its two stretching fundamentals but also several weaker absorptions in the 2000–3600 cm−1 spectral region and a prominent, complicated pattern of absorptions between 3600 and 7800 cm−1. The previous assignment of the 3611 cm−1 HC2 absorption as the CH-stretching fundamental is reviewed, and the assignment of an absorption at 2104 cm−1 as ν2+ν3 of ground-state HC2 is discussed. The near infrared absorption band system has been assigned to the à 2Π–X̃ 2Σ+ transition of HC2, extensively perturbed by interaction with high vibrational levels of the ground state. The position of the transition origin could not be definitively established. The previous assignment of gas-phase absorptions of HC2 at 3786, 4012, and 4108 cm−1 to ground-state combination bands has been confirmed, and carbon-isotopic data have been obtained for these bands. Because all of the HC2 absorptions observed in an argon matrix must originate in the X̃(000) state and because the observed matrix shifts are relatively small, these studies may provide a map to facilitate more detailed gas-phase studies.

The infrared spectroscopy and photochemistry of NO3 trapped in solid neon

“…32 The absorption spectra of the sample deposits were obtained using a Bomem DA 3.002 Fourier-transform interferometer with transfer optics that have been described previously. 33 Most of these observations were conducted with a resolution of 0.2 cm −1 between 450 and 5000 cm −1 using a globar source, a KBr beamsplitter, and a wide band HgCdTe detector cooled to 77 K. Preliminary observations of the 2000-8500 cm −1 spectral region were conducted using a quartz-halogen lamp, a CaF 2 beamsplitter, and an InSb detector cooled to 77 K. Data were accumulated for each spectrum over a period of at least 15 min. The resulting spectrum was ratioed against a similar one taken without a deposit on the cryogenic mirror.…”

The vibrational spectra of CO2+, (CO2)2+, CO2−, and (CO2)2− trapped in solid neon

“…9 Observations were conducted with a resolution and frequency accuracy ͑determined by the Fourier transform data acquisition process͒ of 0.2 cm Ϫ1 between 400 and 5000 cm Ϫ1 using a globar source, a KBr beamsplitter, and a wide-band HgCdTe detector cooled to 77 K. Under these conditions, the positions observed for prominent, nonblended atmospheric water vapor lines between 1385 and 1900 cm Ϫ1 and between 3620 and 3900 cm Ϫ1 agreed within 0.01 cm Ϫ1 with the high-resolution values reported by Toth. 10 Data were accumulated for each spectrum over a period of at least 15 min.…”

The infrared spectrum of NH3-dn trapped in solid neon

“…The absorption spectra of the ammonia deposits were studied using a Bomem DA3.002 Fourier transform interferometer with transfer optics which have previously been described [25]. Observations were conducted with a resolution of 0.2 cm À1 between 400 and 5000 cm À1 using a globar source, a KBr beamsplitter, and a wide-band HgCdTe detector cooled to 77 K. Data were accumulated for each spectrum over a period of at least 15 min.…”