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Progress report from Leicester Stephen Ball & Mark Watkins

Progress report from Leicester Stephen Ball & Mark Watkins. CAVIAR spectroscopists meeting 24 Sept 2009 (Leicester University). New appointment to Leicester CAVIAR postdoc: Dr Mark Watkins. Research Background: Laser Spectroscopy (pulsed lasers): Nanosecond

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Progress report from Leicester Stephen Ball & Mark Watkins

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  1. Progress report from LeicesterStephen Ball & Mark Watkins CAVIAR spectroscopists meeting 24 Sept 2009 (Leicester University)

  2. New appointment to Leicester CAVIAR postdoc: Dr Mark Watkins Research Background: Laser Spectroscopy (pulsed lasers): • Nanosecond • Tuneable lasers: Radiant Dyes, Sirah, Jaguar, LaserVision IR OPO, Panther UV/Vis OPO • Pump lasers: Nd:YAG(Continuum), excimer (Spectra-Physik) • Pico- and Femtosecond • Tuneable solid-state OPO/OPA (TOPAS) • Ti:Sapphire (Spitfire, Mai Tai), Nd:YLF (Evolution and Evolution 30) Weakly bound clusters: • Aromatic, non-aromatic, atomic chromophores • High resolution spectroscopy: REMPI, ZEKE, MATI, OODR • Small molecule and atomic solvents Equipment Design • Design, testing, commissioning and operation

  3. New appointment to Leicester CAVIAR postdoc: Dr Mark Watkins Relevant expertise: Pulsed valve operation: • Bosch fuel injector valve • General Valve (series 9) Vacuum apparatus: • High vacuum operation • Turbomolecular pumps, diffusion pumps, roughing pumps • Vacuum instrumentation Raman spectroscopy (NIR region ~800 nm) • Spectracode instrumentation and CCD imager • Worked industrial patent contracts (Roche, Germany and Santrol, USA) • Developed methods towards real-time mathematical analysis of small (ppt) spectra on large background

  4. CAVIAR pulsed nozzle apparatus: Nozzle Spectrograph/CCD camera LED Up to now: No dimer signal at 620 nm (v = 5 overtone of hydrogen-bonded stretch) Not much water monomer signal at 620 nm either Detection system definitely works!: H2O absorptions when chamber up to atmosphere NO2 absorption features through nozzle

  5. 0.99991 0.99990 0.99989 R(l) 0.99988 0.99987 0.99986 720 730 740 750 760 770 780 790 800 Wavelength / nm Issue #1: v = 5 dimer overtone is v weak Solution: Move to v = 4 overtone around 760 nm (expected x10 stronger) Progress: Done! LED BBCEAS spectra: 70 nm bandwidth, mirror reflectivity calibration Mirror Curve (1200 lines/mm grating, centred at 765 nm) Low resolution spectrum of CO2 “Venus bands” at 782.8 and 789.1 nm 10 km path length in 1 m cavity

  6. Issue #2: Spatial overlap of nozzle expansion with light beam Solution: Point nozzle  slit expansion Progress: Done! Diameter ~ 350 mm Slit width = 12 mm beampath beampath

  7. Issue #3: H2O number density in source gas before: Psat(H2O) = 20 Torr and >1 atm N2 bath gas Solution: Heated nozzle source ~ 60 C after: 150-250 Torr H2O + 0.5-1.0 atm N2 Progress: Heated H2O source built, waiting on thermostat electronics heating collar thermal body H2O reservoir thermocouple General Valve

  8. LED-BBCEAS Issue #4: Temporal overlap of nozzle expansion with light beam Current LED-BBCEAS detection methodology is CW Solution: Pulsed detection methodology: Cambridge BBCRDS system Pulsed laser and clocked CCD camera synchronised to nozzle Progress: Equipment loan arranged for October  Pulsed nozzle Pulsed nozzle: rep rate 20 Hz, 180 – 300 ms opening time Pulsed laser BBCRDS Pulsed nozzle

  9. Photoacoustic Experiment? Timescale: 1 – 3 days Oscilloscope Water vapour spectrum (taken in air) Pulsed IR laser (OPO/OPA)

  10. Timetable for experimental work @ Leicester

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