Double-resonance spectroscopy of small molecules using an optical frequency comb

Satellite- and ground-based observations of hot-Jupiter exoplanets reveal the presence of molecular species in their atmospheres. The observed spectra carry information about the thermodynamic conditions and chemistry on those exoplanets. To extract it, we need accurate theoretical models of the spectra verified by high-precision laboratory measurements.

However, the accuracy of theoretical high-temperature molecular line lists is often poor, because of the lack of reference experimental data.

We will use sub-Doppler double-resonance spectroscopy with a continuous wave pump and a frequency comb probe to measure and assign transitions to highly excited levels of methane, ammonia and acetylene with unprecedented combination of bandwidth, resolution and sensitivity.

Using different pump/probe combinations we will address hundreds of transitions to yet unexplored states in the 9000-12000 cm-1 energy range.

High absorption sensitivity will be obtained by the use of enhancement cavities, and the comb spectra will be recorded using a Fourier transform spectrometer.

Our project will provide data needed to improve the accuracy of the theoretical models used to interpret the high-temperature spectra of hot-Jupiter exoplanets and other astronomical objects.

This, in turn, will contribute to new scientific discoveries by the planned NASA and ESA missions that will investigate the exoplanetary atmospheres using high-resolution infrared spectroscopy.