Vibrational satellites of C₂S, C₃S, and C₄S: microwave spectral taxonomy as a stepping stone to the millimeter-wave band

Abstract

We present a microwave spectral taxonomy study of several hydrocarbon/CS2 discharge mixtures in which more than 60 distinct chemical species, their more abundant isotopic species, and/or their vibrationally excited states were detected using chirped-pulse and cavity Fourier-transform microwave spectroscopies. Taken together, in excess of 85 unique variants were detected, including several new isotopic species and more than 25 new vibrationally excited states of C2S, C3S, and C4S, which have been assigned on the basis of published vibration-rotation interaction constants for C3S, or newly calculated ones for C2S and C4S. On the basis of these precise, low-frequency measurements, several vibrationally exited states of C2S and C3S were subsequently identified in archival millimeter-wave data in the 253-280 GHz frequency range, ultimately providing highly accurate catalogs for astronomical searches. As part of this work, formation pathways of the two smaller carbon-sulfur chains were investigated using 13C isotopic spectroscopy, as was their vibrational excitation. The present study illustrates the utility of microwave spectral taxonomy as a tool for complex mixture analysis, and as a powerful and convenient 'stepping stone' to higher frequency measurements in the millimeter and submillimeter bands.

Alternation of Singlet and Triplet States in Carbon‐Based Chain Molecules and Its Astrochemical Implications: Results of an Extensive Theoretical Study

“…Emphasizing that most stable isomers of carbon‐based chains of the type considered in our paper are not invariably singlets is important because this was incorrectly claimed in some recent studies done in the astronomical/astrophysical community . Prior to the present extensive study, a series of authors drew attention on the fact that triplet isomers of carbon‐based chains are more stable than singlet isomers: HCH, C 2 k , HC 4 N, NC 5 N, C 2 k O, C 2, 4 S, and HC 6 N …”

Building Blocks of Dust and Large Organic Molecules: A Coordinated Laboratory and Astronomical Study of Agb Stars

“…Precise rest frequencies have also been reported for a number of the more abundant isotopic species at millimeter-wave and submillimeter-wave wavelengths 19. For SiO18,22 and to a lesser extent CS,23,24 the same is true, however, the laboratory measurements for SiC are significantly more limited, although the pure rotational transitions from the 3 Π ground state and v = 1 have been observed in the millimeter-wave band, as has lines of ground state 29 SiC and Si 13 C 25. Those up to v = 5 for normal SiC were derived at somewhat lower resolution by Butenhoff and Rohlfing26 by laser-induced fluorescence excitation spectroscopy, but very little high-resolution spectroscopy of this radical has been reported since the early 1990s.…”

Generation and structural characterization of Ge carbides GeCn (n = 4, 5, 6) by laser ablation, broadband rotational spectroscopy, and quantum chemistry

“…Chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy 35 followed by its cavity variant 36 were used to de- tect and analyze products formed in the laser ablation of a Ge:C rod. The combined approach of CP-and cavity FT spectroscopy has recently been used with good success to detect entirely new molecules, 37 such as HC 4 C(O)H, 38 GeC 2 , 19 and new vibrationally excited states of highly abundant species, such as C 2 S and C 3 S. 39 A real strength of this approach is that it exploits the advantages of both spectroscopies, in which the CP spectrum is used as a survey tool to detect "bright" resolution elements over a very wide frequency range, and cavity spectroscopy can then be efficiently used to rapidly analyze and characterize these smaller number of spectral features, owing to its higher instantaneous sensitivity and spectral resolution.…”