Patrick Dupré

The contemporary spectroscopy of gas targets several objectives, such as the fine description of the molecular Hamiltonians, the trace detection of diverse species, and the fundamental physics. In simple molecules such as molecular hydrogen, the transitions between energy levels can be probed to test the Standard Model of the Physics (i.e., the Quantum ElectroDynamics), and beyond. For example, the proton-to-electron mass ratio and the proton-radius size can be challenged. On other side, the detection of trace of molecules is of crucial importance for understanding chemical processes and molecular line shape. Up-to-date spectroscopy techniques based on optical cavities associated with Optical Frequency Combs have been developed in the Near-Infrared range to challenge sensitivity and frequency precision. We will illustrate the capability of the Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS), from both theoretical and experimental approaches. Very recent results on a few molecular species (C2H2 and HD) will be discussed for questioning the ultimate resolution and sensitivity which can be targeted.