Fano-like resonance due to interference with distant transitions

TL;DR

This paper introduces a new Fano-like resonance mechanism caused by interference with distant energy levels, verified through Doppler-free spectroscopy of CO₂, with implications for precision measurements and optical technologies.

Contribution

It proposes and experimentally demonstrates a novel Fano-like resonance mechanism involving distant levels, expanding understanding of spectral line profiles in atomic and molecular systems.

Findings

Observed asymmetric spectral profiles consistent with Fano-like interference

Resonance amplitude scales quadratically with laser power

Verified mechanism using Doppler-free spectroscopy of CO₂ transitions

Abstract

Narrow optical resonances of atoms or molecules have immense significance in various precision measurements, such as testing fundamental physics and the generation of primary frequency standards. In these studies, accurate transition centers derived from fitting the measured spectra are demanded, which critically rely on the knowledge of spectral line profiles. Here, we propose a new mechanism of Fano-like resonance induced by distant discrete levels %in atoms or molecules and experimentally verify it with Doppler-free spectroscopy of vibration-rotational transitions of CO$_2$. The observed spectrum has an asymmetric profile and its amplitude increases quadratically with the probe laser power. Our results facilitate a broad range of topics based on narrow transitions. %, such as optical clocks, determination of fundamental physical constants, and quantum memory.