title: Ortho-Para-Dependent Pressure Effects Observed in the Near Infrared Band of Acetylene by Dual-Comb Spectroscopy.
abstract: We demonstrate that dual-comb spectroscopy, which allows one to record broadband spectra with high frequency accuracy in a relatively short time, provides a real advantage for the observation of pressure-broadening and pressure-shift effects. We illustrate this with the ν_{1}+ν_{3} vibration band of ^{12}C_{2}H_{2}. We observe transitions from P(26) to R(29), which extend over a 3.8 THz frequency range, at six pressures ranging up to 2654 Pa. Each observed absorption line profile is fitted to a Voigt function yielding pressure-broadening and pressure-shift coefficients for each rotation-vibration transition. The effectiveness of this technique is such that we are able to discern a clear dependence of the pressure-broadening coefficients on the nuclear spin state, i.e., on the ortho or para modification. This information, combined with the pressure-shift coefficients, can facilitate a detailed understanding of the mechanism of molecular collisions.
authors.affiliation: Department of Physics, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.|National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8563, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Iwakuni
authors.affiliation: National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8563, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Okubo
authors.affiliation: Environmental Management Research Institute (EMRI), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan.
authors.forename: Koichi M T
authors.initials: KM
authors.lastname: Yamada
authors.affiliation: National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8563, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Inaba
authors.affiliation: National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8563, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Onae
authors.affiliation: National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8563, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.|Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan.
authors.forename: Feng-Lei
authors.initials: FL
authors.lastname: Hong
authors.affiliation: Department of Physics, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.|JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, Tsukuba 305-8563, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sasada