title: Direct measurements of collisional Raman line broadening in the S-branch transitions of acetylene (C2H2).
abstract: We report direct measurements of the self- and N2-broadened Raman S-branch linewidths of acetylene (C2H2), obtained by employing time-resolved picosecond rotational coherent anti-Stokes Raman scattering spectroscopy. Using broadband 115-ps pump and Stokes pulses (~135 cm(-1) bandwidth) and a spectrally narrowed 90-ps probe pulse (~0.2 cm(-1) bandwidth), Raman-coherence lifetimes are measured at room temperature for the S-branch (ΔJ = +2) transitions associated with rotational quantum number J = 3-25. These directly measured Raman-coherence lifetimes, when converted to collisional linewidth broadening coefficients, differ from the previously reported broadening coefficients extracted from theoretical calculations by 6%-35% for self-broadening for C2H2 and by up to 60% for N2-broadened C2H2.
authors.affiliation: Spectral Energies, LLC, 5100 Springfield Street, Suite 301, Dayton, Ohio 45431, USA.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Hsu
authors.forename: Hans U
authors.initials: HU
authors.lastname: Stauffer
authors.forename: Naibo
authors.initials: N
authors.lastname: Jiang
authors.forename: James R
authors.initials: JR
authors.lastname: Gord
authors.forename: Sukesh
authors.initials: S
authors.lastname: Roy