Raman and far infrared spectra of crystalline acetylene, C₂H₂ and C₂D₂

Abstract

Raman and far infrared spectra of the orthorhombic and cubic phases of acetylene and deuterated acetylene have been obtained. In the orthorhombic phase, three of the four expected librations have been identified in the Raman spectrum and the two infrared active translations have been confirmed, for both samples. In the cubic phase, two of the three predicted librations in the Raman spectrum and the expected pair of translations in the far infrared spectrum have been observed, again for both samples. Splittings in the internal mode Raman spectra are, with one exception, in agreement with the predictions of group theory.

Desorption Kinetics and Binding Energies of Small Hydrocarbons

“…These "bumps" may be due to an amorphous-to-crystalline transition. There are studies that have constrained the temperatures at which amorphous-tocrystalline transitions are expected to occur for 2-carbon hydrocarbons (e.g., Anderson et al 1985;Khanna et al 1988;Zhao et al 1988;Hudson et al 2014a,b), and these are generally consistent with the temperature points of the "bumps" in our pure 2-carbon TPD curves (Fig. 2).…”

Properties and Behavior of the Acetonitrile–Acetylene Co-Crystal under Titan Surface Conditions

“… a Assignments from the published report for pure acetylene b Pure orthorhombic C 2 H 2 spectrum collected at 100 K. c Orthorhombic C 2 H 2 at 30 K d sI clathrate hydrate, large cage, collected at 90 K …”

Infrared spectra and optical constants of astronomical ices: I. Amorphous and crystalline acetylene

“…The warming or cooling rate was about 3 K min À1 . Each ice's single-beam spectrum was ratioed against the background (blank) spectrum of the KBr substrate recorded at the same temperature, maintained with a precision of ±0.3 K. As discussed by Anderson et al (1985) and Khanna et al (1988), the IR and Raman spectra of C 2 H 2 ice formed at 70 K are suggestive of an orthorhombic crystalline structure. Although a transition to a cubic crystalline phase occurs at 133 K (Smith, 1969), it was not studied in our work since C 2 H 2 ice rapidly sublimes above 80 K in our vacuum system.…”

“…We suspect that in each attempt a fraction of amorphous material remained. The purely-crystalline phase Herman et al (2003), with assistance from Plyler et al (1963), Bottger and Eggers (1964), and Anderson et al (1985). Some assignments, particularly those form > 4000 cm À1 , should be regarded as tentative.…”