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Description
The reaction between carbon atoms and vinyl cyanide, CH_2_CHCN, is a possible formation route for interstellar 3-cyano propargyl radical, CH_2_C_3_N. 1-Cyano propargyl radical (HC_3_HCN), an isomer of CH_2_C_3_N, is predicted to be produced in the same reaction at least twice more efficiently than CH_2_C_3_N. Hence, HC_3_HCN is a plausible candidate to be observed in space as well. We aim to generate HC_3_HCN radical in the gas phase in order to investigate its rotational spectrum. The derived spectroscopic parameters for this species will be use to obtain reliable frequency predictions to support its detection in the space. Rotational spectrum of HC_3_HCN radical was produce by electric discharges and characterized using a Balle-Flygare narrowband type Fourier-transform microwave (FTMW) spectrometer operating in the frequency region of 4-40GHz. The spectral analysis was supported by high-level ab initio calculations. A total of 193 hyperfine components originated from twelve rotational transitions, a- and b-type, were measured for HC_3_HCN radical. The analysis allowed us to accurately determine twenty-two molecular constants, including rotational and centrifugal distortion constants as well as the fine and hyperfine constants. Transition frequency predictions were used to search for HC_3_HCN radical in TMC-1 using the QUIJOTE survey between 30.1-50.4GHz. We can not confirm the presence of HC_3_HCN in TMC-1 and obtain an upper limit to the column density of HC_3_HCN in TMC-1 of 6.0*10^11^cm^-2^.
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