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Updated: Aug 13, 2026

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Double-resonance spectroscopy determines highly excited vibrational energy of 13CO2 with kilohertz accuracy
Tian-Hu Liu1, Yan-Dong Tan1, Cun-Feng Cheng1,2
1Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.
Abstract:
We present a comb-referenced mid-infrared to near-infrared double-resonance (MIR-NIR DR) scheme applied to 13CO2 to achieve high-accuracy rovibrational term values for highly excited, optically dark vibrational states. A single-pass MIR pump drives the strong ν3 = 1 ← 0 fundamental transition, while a cavity-enhanced NIR probe interrogates the weak ν3 = 4 ← 1 hot band via ring-down detection. Using a ladder (Ξ)-type excitation scheme that links the ground state directly to the 4ν3 manifold, the sum of the two transition frequencies yields the pure vibrational energy of the dark (00 041) state with an uncertainty of 4.0 kHz, providing metrology-grade constraints for theoretical models and line lists. The demonstrated approach offers a practical route to access dark or ultra-weak vibrational manifolds in molecules of atmospheric and astrophysical relevance.
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