Acetylene, 12C2H2: new CRDS data and global vibration-rotation analysis up to 8600 cm-1

Abstract

The absorption spectrum of 12 C 2 H 2 has been recorded using cavity ringdown spectroscopy and analyzed in the ranges 6000 À 6356 cm À1 and 6667À7015 cm À1 . Fourteen new bands have been identified and additional J-lines were assigned in 10 already known bands. These new data, together with the published vibration-rotation absorption lines of 12 C 2 H 2 accessing vibrational states up to 8600 cm À1 have been gathered in a database. The resulting set includes 12137 transitions involving 186 different k ¼ l 4 þ l 5 sub-states, with l i the angular momentum quantum number associated to the i degenerate bending vibration. These lines have been fitted simultaneously to spectroscopic parameters through J-dependent Hamiltonian matrices exploiting the vibrational polyad or cluster block-diagonalization, in terms of the pseudo-quantum numbers N r ¼ 5v 1 þ 3v 2 þ 5v 3 þv 4 þv 5 and N s ¼ v 1 þ v 2 þ v 3 , also accounting for k and e/f parities and u/g symmetry. Modes 1 and 2 correspond to the symmetric CH and CC stretchings, mode 3 to the antisymmetric CH stretch, and modes 4 and 5 to the trans-and cis-degenerate bendings, respectively. The fit was successfully achieved, with a dimensionless standard deviation of 0.92, leading to the determination of 266 effective vibration-rotation parameters.

High resolution overtone spectroscopy of the acetylene van der Waals dimer, (12C2H2)2

“…It is unlikely that these perturbations are carried over from the monomer since they are tunneling-symmetry-dependent in the dimer, and also because the coupling network in the monomer is very complex and diffuse. 20,21 One can only suggest that, depending on if a full or a limited series of J-levels is affected, the interaction mechanism is of anharmonic resonance or Coriolis type, respectively. The first category includes most perturbations reported.…”

A four-atom molecule at the forefront of spectroscopy, intramolecular dynamics and astrochemistry: Acetylene

“…Others used Fourier transform interferometers (FTIR) [15], sometimes with synchrotron radiation [16] or femtosecond laser [17] absorption sources. Others laser techniques such as opto acoustic laser (OAS) [18], continuous-wave cavity ring down (CW-CRDS) [19] and intracavity laser absorption (ICLAS) [20] spectroscopies, the latter sometimes with FTIR detection [21]. Some initial applications of less conventional techniques were also made with acetylene.…”

Acetylene, 12C2H2: Refined analysis of CRDS spectra around 1.52μm

“…We previously reported on the analysis of spectra of 12 C 2 H 2 around the m 1 + m 3 band in the 1.5 lm spectral range recorded using cavity ring down spectroscopy (CRDS) [1]. The detection sensitivity using CRDS was significantly increased compared to that of conventional Fourier transform infrared experiments previously reported in the literature in this spectral range [2][3][4][5][6][7].…”

“…The CRDS spectra presently analysed were already presented in [1]. The fibered CW-CRDS spectrometer and the procedure adopted for an accurate calibration of the wavenumber scale of the recorded spectra, in Grenoble, were described in [13][14][15].…”