title: Absolute density measurement of SD radicals in a supersonic jet at the quantum-noise-limit.
abstract: The absolute density of SD radicals in a supersonic jet has been measured down to (1.1 ± 0.1) × 10(5) cm(-3) in a modestly specified apparatus that uses a cross-correlated combination of cavity ring-down and laser-induced fluorescence detection. Such a density corresponds to 215 ± 21 molecules in the probe volume at any given time. The minimum detectable absorption coefficient was quantum-noise-limited and measured to be (7.9 ± 0.6) × 10(-11) cm(-1), in 200 s of acquisition time, corresponding to a noise-equivalent absorption sensitivity for the apparatus of (1.6 ± 0.1) × 10(-9) cm(-1) Hz(-1/2).
authors.affiliation: Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK. david.carty@durham.ac.uk.
authors.forename: Arin
authors.initials: A
authors.lastname: Mizouri
authors.forename: L Z
authors.initials: LZ
authors.lastname: Deng
authors.forename: Jack S
authors.initials: JS
authors.lastname: Eardley
authors.forename: N Hendrik
authors.initials: NH
authors.lastname: Nahler
authors.forename: Eckart
authors.initials: E
authors.lastname: Wrede
authors.forename: David
authors.initials: D
authors.lastname: Carty
mesh_terms: D000401:Aircraft; D005609:Free Radicals / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
chemical_list: D005609:Free Radicals; D009584:Nitrogen