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Updated: Mar 31, 2026

ARL Spectral Fitting as an Application to Augment Spectral Data via Franck-Condon Lineshape Analysis and Color Analysis
Published on: August 19, 2021
Accurate lineshape spectroscopy and the Boltzmann constant
G-W Truong1,2, J D Anstie1,2, E F May3
1Institute for Photonics and Advanced Sensing (IPAS) and School of Chemistry and Physics, The University of Adelaide, Adelaide, South Australia 5005, Australia.
This study introduces a quantum-limited spectrometer for high-precision spectroscopy. It accurately measures cesium hyperfine splitting and determines Boltzmann
Area of Science:
- Quantum spectroscopy
- Atomic physics
- Metrology
Background:
- Spectroscopy is crucial for scientific discovery and testing physical theories.
- Achieving fundamental-noise limits enhances spectroscopic information extraction.
- Existing spectral profiles like the Voigt profile have limitations.
Purpose of the Study:
- To demonstrate a quantum-limited spectrometer for high-precision absorption measurements.
- To accurately measure the excited-state hyperfine splitting in Cesium (Cs).
- To investigate and model deviations from the standard Voigt spectral profile.
Main Methods:
- Development and application of a quantum-limited spectrometer.
- High-precision measurement of Cesium absorption lineshapes.
- Theoretical modeling to explain observed spectral profile breakdowns.
Main Results:
- Demonstrated a quantum-limited spectrometer achieving high-precision measurements.
- Accurately measured the excited-state (6P1/2) hyperfine splitting in Cs.
- Observed and theoretically explained a breakdown in the Voigt spectral profile.
Conclusions:
- The developed model explains spectral profile deviations within the shot-noise limit.
- Inferred thermal velocity dispersion of Cs vapor with 35 p.p.m. uncertainty.
- Determined Boltzmann's constant with 6 p.p.m. precision and 71 p.p.m. uncertainty.
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