title: Background-free coherent anti-stokes Raman scattering of gas- and liquid-phase samples in a mesoporous silica aerogel host.
abstract: Efficient time-resolved coherent anti-Stokes Raman scattering (CARS) of atmospheric nitrogen and ethanol trapped in a nanoporous silica aerogel matrix is demonstrated. Silica aerogel hosts are attractive for analytical CARS spectroscopy due to their high porosity/low density, low refractive index, and low scattering cross-section. Differences between the resonant and nonresonant parts of the nonlinear optical susceptibilities lead to much longer relaxation times for analytes compared to the matrix. Time-resolved CARS can then be used to obtain a nearly background-free measurement at characteristic vibrations of the analyte. These results demonstrate the potential of this approach for rapid, sensitive, background-free analyses of analytes entrapped in the aerogel pores, which may be advantageous for some environmental, chemical, and biological sensing applications.
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada.
authors.forename: Stanislav O
authors.initials: SO
authors.lastname: Konorov
authors.forename: Robin F B
authors.initials: RF
authors.lastname: Turner
authors.forename: Michael W
authors.initials: MW
authors.lastname: Blades