A laboratory rotational study of the interstellar propynal

Abstract

The discovery of propynal HCCCHO in the interstellar medium (ISM), has been reported in previous investigations, but its detection relied on only a few measured rotational transitions. Therefore, we provide in this work an exhaustive experimental study of its rotational spectra in the microwave, millimeter-wave (mm-wave), and sub-millimeter wave (sub-mm) regions from 6 to 480 GHz. We employed different but complementary spectroscopic techniques in the time and frequency domains. Chirped pulse Fourier transform microwave spectroscopy (CP-FTMW) from 6 to 18 GHz was used to measure and analyze the ground state rotational transitions of the three 13C isotopic species in their natural abundances. The Stark-modulation microwave spectroscopy allowed the identification of rotational spectra in excited vibrational states. The room temperature mm-wave and sub-mm wave spectroscopy made possible the study of the rotational spectra from 82 to 480 GHz in the ground state as well as in the five low-lying excited vibrational states. We have collected more than 2500 newly assigned transitions of propynal and determined very accurate sets of spectroscopic rotational constants for each state. Moreover, we have assigned about 200 rotational lines for the three 13C isotopologues. Reliable line-lists of frequencies are provided for further observations of this molecule in different interstellar regions.