Millimeter-millimeter-wave double-modulation double-resonance spectroscopy

TL;DR

This paper introduces a novel millimeter-wave double-modulation double-resonance spectroscopy technique that enhances the detection and assignment of complex molecular spectra, especially in dense astronomical spectra, with potential for automation.

Contribution

The paper presents a new MMW-MMW DM-DR method that improves spectral clarity and transition identification in complex organic molecules, demonstrating its advantages over traditional techniques.

Findings

Unambiguous assignment of weak and blended transitions.

Effective identification of target lines in dense spectra.

Observation of Autler-Townes line splitting.

Abstract

A new millimeter- to millimeter-wave double-modulation double-resonance (MMW-MMW DM-DR) scheme has been applied to record spectra of two astronomically relevant complex organic molecules (COMs), propanal (C2H5CHO) and ethyl cyanide (C2H5CN), to demonstrate advantages of the DM-DR experimental technique. The DR technique helps to identify target transitions in a forest of lines and the implementation of a DM procedure (modulation of the pump and probe source) allows for confusion- and baseline-free spectra containing only the line(s) of interest. In particular the unambiguous assignment of weak and blended transitions in very dense MMW spectra is highlighted. Details of the observed Autler-Townes line splitting and possible future applications, such as automated analyses and adaptions of DM-DR methods to other experimental setups, are discussed.