Differential chirped-pulse dual-comb spectroscopy for complex line shape fitting the R(6) manifold of the 2ν3 band of methane

Published

March 25, 2025

Author(s)

Jasper Stroud, David Plusquellic

Abstract

In this manuscript, we use a dual electro-optic comb system (EO-OFC) and a differential chirped-pulse down conversion technique to study the R(6) manifold of the 2ν3 band (1645 nm) of methane at low pressure (< 1 kPa). In the frequency domain, the EO-OFC method magnifies of the temporal dynamics of the system and because of the 6-component asymmetric line shape, is shown to give unique amplitude and phase spectra that depend on the chirp direction. We model the frequency domain complex response function using chirped-pulse multiplication and convolution with the transfer function of the molecular system. We then compare how the predicted line shapes from HITRAN 2012 and HITRAN 2020 databases and from the Hartmann-Tran profile (HTP) perform for fitting both the temporally magnified magnitude and phase profiles in the frequency domain and following the removal of these effects from back transformation, the traditional (natural) line shape components in the time domain. The time domain phase profile is not adequately predicted and since the temporally magnified amplitude and phase components become mixed in the rapid down conversion process, the fit residuals are shown to give unusually large discrepancies in the HTP amplitude and phase spectra. Nevertheless, the HTP has the best overall fit residuals of magnitude spectrum for the highest resolution data obtained. The complex responses in the two domains have given unique insight into the physical nature of the models that may help guide future developments to improve their predictive behavior of amplitude and phase.

Citation

Journal of Quantitative Spectroscopy and Radiative Transfer

Volume

340

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.jqsrt.2025.109454

Local Download

Keywords

Dual comb, electro-optic combs, Hartmann-Tran, magnitude, phase

Citation

Stroud, J. and Plusquellic, D. (2025), Differential chirped-pulse dual-comb spectroscopy for complex line shape fitting the R(6) manifold of the 2&#957;3 band of methane, Journal of Quantitative Spectroscopy and Radiative Transfer, [online], https://doi.org/10.1016/j.jqsrt.2025.109454, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958875 (Accessed May 20, 2025)