Publication Date:
2018-06-06
Description:
Our present knowledge of the molecular universe has come primarily from radio observations [ I include here millimeter and submillimeter in this rubric]. There are a number of reasons for this but the primary one is the extremely high spectral resolution. The ease of observing emission from the volume of dense molecular clouds without significant attenuation by scattering from dust has shown this to be the powerful observational tool for molecular astronomy. Finally the relative simplicity of rotational compared to vibrational or electronic spectroscopy allows carrier identification as well as facile evaluation of cloud conditions such as density and temperature. These virtues become tenuous as the astronomical observations are pushed to higher frequencies for enhanced observational sensitivity. Thus precision rest frequencies are mandatory for the search for new species. We may inquire about which new species require particular attention, and which species may be relatively safely predicted on the basis of lower frequency laboratory measurements. For a rigid rotor the three rotational constants are sufficient to completely specify the transition frequencies. The intensities require the three components of the electric dipole moment. For semirigid species, where the centrifugal distortion, may be treated at the quartic level of angular momentum (Bunker et al. 1998), up to five additional constants are required (Watson 1967). There are a number of such species of considerable interest, where laboratory measurements are adequate for astronomical searches.
Keywords:
Astrophysics
Type:
Proceedings of the NASA Laboratory Astrophysics Workshop; 133-135; NASA/CP-2006-214549
Format:
application/pdf
