Description
Two hundred and fifty-one ^12^C_2_D_2_ transitions have been measured in the 0.2-1.6THz region of its nu_5_-nu_4_ difference band and 202 of them were observed for the first time. The accuracy of these measurements is estimated to be ranging from 50kHz to 100kHz. The ^12^C_2_D_2_ molecules were generated under room temperature by passing 120-150mTorr D_2_O vapor through calcium carbide (CaC_2_) powder. A multistate analysis was carried out for the bending vibrational modes nu_4_ and nu_5_ of ^12^C_2_D_2_, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for ^12^C_2_D_2_ by adding the new measurements to the old data set, which had only 10 lines with microwave measurement precision. New frequency and intensity predictions have been made based on the obtained molecular parameters. The more precise measurements and new predictions reported here will support the analyses of astronomical observations by the future high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA, which will work in the terahertz spectral region.
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