Pure Rotational Spectrum and Electric Dipole Moment of CH3D

Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1. A study of the isomers of C5H4

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ~4-15. For this species, we derived a rotational temperature of 7±1K and a column density of 1.2±0.2×1013 cm-2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr=7.0±0.3 K, and a column density for its two states (A and E) of 6.5±0.3×1012 cm-2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a3σ upper limit of 2.5×1012 cm-2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

On the Rotational Analysis of the Ground Vibrational State of CH3D Molecule

The rotational analysis in the ground vibrational state has been carried out for CH3D by using the ground state combination differences. More than 1500 allowed and 2500 forbidden transitions from the fundamental bands nu3, nu5, and nu6 were used to determine 12 rotational parameters, which reproduce the observed combination differences within an accuracy of 1.0 x 10(-4) cm-1. Altogether ten independent a1-a2 (K = 3) splittings with J >/= 10 in the vibrational ground state were observed and analyzed both with supercombination differences method [O. N. Ulenikov, S. Alanko, M. Koivusaari, and R. Anttila, Chem. Phys. Lett. 268, 242-248 (1997)] and by generating energy levels from Hamiltonian. Problems in simultaneous determination of epsilon; and &htilde;3 constants responsible for such splittings are discussed. Copyright 1999 Academic Press.

AFGL atmospheric absorption line parameters compilation: 1982 edition

The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 cm(-1), improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-microm bands of methane. The atlas now contains approximately 181,000 rotation and vibration-rotation transitions between 0 and 17,900 cm(-1). The sources of the absorption parameters are summarized.