title: A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. II. Performance and applications for reaction dynamics.
abstract: This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in pulsed uniform flows. Here we detail the development and testing of a new K(a)-band CP-FTMW spectrometer in combination with the pulsed flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys. 141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Chamara
authors.initials: C
authors.lastname: Abeysekera
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Lindsay N
authors.initials: LN
authors.lastname: Zack
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: G Barratt
authors.initials: GB
authors.lastname: Park
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Joalland
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Oldham
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Kirill
authors.initials: K
authors.lastname: Prozument
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Nuwandi M
authors.initials: NM
authors.lastname: Ariyasingha
authors.affiliation: Institut de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes Cedex, France.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sims
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Field
authors.affiliation: Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.
authors.forename: Arthur G
authors.initials: AG
authors.lastname: Suits