Ultra-resolution photochemical sensing

TL;DR

This paper presents a novel ultra-resolution ultraviolet dual comb spectroscopy technique that significantly improves the accuracy of measuring formaldehyde's absorption cross sections, enhancing atmospheric pollutant monitoring and quantum simulations.

Contribution

It introduces a high-resolution, broad-coverage spectroscopic method that uncovers more molecular transitions and refines quantum models for atmospheric sensing.

Findings

Uncovered nearly ten times more rovibrational transitions in formaldehyde.

Achieved spectral resolution of 1 GHz and broad coverage of 12 THz.

Provided refined rotational constants for molecular simulations.

Abstract

Photochemistry in the earth's atmosphere is driven by the sun, continuously altering the concentration and spatial distribution of pollutants. Precisely monitoring their atmospheric abundance relies predominantly on optical sensing, which requires the knowledge of exact absorption cross sections. One key pollutant which impacts many photochemical reaction-pathways is formaldehyde. Agreement on formaldehyde absolute absorption cross section remains elusive in the photochemically-relevant ultraviolet spectral region, hampering sensitive concentration tracking. Here, we introduce free-running ultraviolet dual comb spectroscopy, combining high spectral resolution (1 GHz), broad spectral coverage (12 THz), and fast acquisition speed (500 ms), as a novel method for absolute absorption cross section determination with unprecedented fidelity. Within this bandwidth, our method uncovers almost one order of magnitude more rovibrational transitions than detected before which leads to refined rotational constants for high-level quantum simulations of molecular eigenstates. This ultra-resolution method can be generalized to provide a universal tool for fast electronic fingerprinting of atmospherically-relevant species, both for sensing applications and to benchmark improvements of ab-initio quantum theory.