Rotational Spectroscopy of Urea up to 500 GHz: The Ground State and Eight Excited Vibrational States

The significance of urea in the formation of complex prebiotic molecules has made it an appealing target for astronomers searching for precursors to life in space [1]. Some of the data presented here has enabled definitive detection of interstellar urea with modern submillimeter telescopes [2]. Assignment of the ground and eight lowest vibrational states of urea, (NH2)2CO, was performed between 210-500 GHz [3]. Intensities of the excited state lines were calibrated by means of a global fit of the ground state and excited state intensities to determine relative vibrational energies. The lowest of these states was found to be 61 cm−1 above the ground state agreeing with previously determined values and could be of use in the determination of the temperature urea spectra. Many of the excited vibrational states were found to be significantly coupled and were treated in the fit. Combined, vibrational symmetries along with the relative energies provide insight into the structure of urea vibrational energies.

[1] A. J. Remijan et al., “OBSERVATIONAL RESULTS OF A MULTI-TELESCOPE CAMPAIGN IN SEARCH OF INTERSTELLAR UREA [(NH2)2CO],” Astrophys J, vol. 783, no. 2, p. 77, 2014

[2] A. Belloche et al., “Re-exploring Molecular Complexity with ALMA (ReMoCA): interstellar detection of urea,” Astron & Astrophys, vol. 628, 2019

[3] D. J. Tyree, T. W. Chapman, I. R. Medvedev, and Z. Kisiel, “Rotational spectroscopy of urea up to 500 GHz: The ground and eight excited vibrational states,” J Mol Spectrosc, vol. 390, p. 111706, 2022