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Description
At least a dozen molecules with a formyl group (HCO) have been observed to ate in the interstellar medium (ISM), suggesting that other such species exist nd await discovered. However there is still a lack of high-resolution spectroscopic data for simple molecular species of this type that could provide basis for their detection. Cyclopropanecarboxaldehyde, c-C_3_H_5_CHO, is a small molecule containing a formyl group and is an interesting candidate for astrophysical detection. The rotational spectrum of cyclopropanecarboxaldehyde has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the ISM. We measured the rotational spectrum of cyclopropanecarboxaldehyde in the frequency ranges 31.5-50GHz and 72-116.5GHz using the GACELA (GAS CEll for Laboratory Astrophysics) broadband high resolution rotational spectrometer constructed at the Yebes Observatory. The spectroscopic study was supported by high-level theoretical calculations which were used in the identification of the vibrational excited states of cyclopropanecarboxaldehyde. The analysis of the rotational spectrum of cyclopropanecarboxaldehyde allowed us to obtain accurate rotational parameters for the ground state of both cis and trans isomers, which were used to derive predictions sufficiently reliable up to 500GHz. In addition to the ground states, we identified twelve and six vibrationally excited states for the trans and cis isomers, respectively, including fundamental modes, multiple excitation quanta and combination states. We found that the gas phase concentration of the trans isomer is almost 1.2 times larger than that for the cis one. The new experimental rotational parameters were employed to search for cyclopropanecarboxaldehyde in the warm molecular clouds Orion KL and Sgr B2(N) using the spectral surveys captured by ALMA (Orion) and IRAM 30m (Sgr) at 1mm and 3mm, respectively.
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