Survey of Molecular Rotational Transitions for Millimeter-Wave Frequency Metrology.

User-defined, spectrally pure and tunable millimeter-wave oscillators, using emerging photonic technologies, enables the probing of pure rotational molecular transitions (from 30 GHz to 1 THz). This work promises to open new applications in frequency metrology, precision molecular spectroscopy, and trace gas sensing. Here we report a theoretical survey of a wide range of molecular candidates to compare their suitability for use in a rotational based clock. We will report calculations that lead to theoretical estimations of clock factors of interest such as line positions and strengths, and sensitivity to environmental perturbations. This work will provide an understanding of the utility of ultra-precise measurements of the rotational spectrum in blooming applications such as radio-astronomy and remote sensing, non-invasive sensing, wireless communications, and for THz frequency metrology.