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Download Atomic and Molecular Physics Ultrafast Laser Physics and Laser Spectroscopy Instrumentation seminar Femtosecond spectroscopy Ultrafast gas phase phenomena

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  • Atomic and Molecular PhysicsUltrafast Laser Physics and Laser SpectroscopyInstrumentation seminar Femtosecond spectroscopyUltrafast gas phase phenomenaFemtochemistryLaser SpectroscopyLaser physics on surfacesPSP-investigations

  • PersonnellFemtosecond spectroscopyUltrafast gas phase FemtochemistryLaser SpectroscopyLaser physicsSonoluminiscence PSP-investigations

    Lars-Erik Bergsa LarssonRene AnderssonNiklas GadorMing LiuPeter SalnBo Zhang

    Marica SjdinNils Tillmark MTimmy Sigfrids MNathan Ross FOI

    Mats Larsson SUTony Hansson Peter vd MeulenPeder Royen Pia Johansson

  • Fast Phenomena

    TimescaleBandwidth10-1510-1410-1310-1210-11100 nm1 nmWavetrain3 mm3 mmfspssFast Phenomena

  • Interested visitor at the fs-labNiklasBoPiaGran

  • Femtosecond spectroscopy The advent of the laser in 1960 and the development of thefemtosecond laser with Dt = 100 fs in 1990 led to:

    * hope that the lasers can steer chemical reactions* hope that final products can be selected* the fs laser excites molecules and probes the pot. surfaces* the fs laser exites molecules in studies of decay channels* the fs laser can excite quantum well semiconductor surfaces giving information about mesoscopic structures* few experiments done reveal real-time evolution

  • Vibration of small molecules .. rt = 0t = T/2t = T0T2TtOscillation period T~ 100 fsrV

  • Fragmentation of molecules rrVA + BA* + B1 in 50 fs

  • Collisions atoms - atoms rArAr+10 eV - 10 keVTimescale 100 fs - 1 fs

  • Other Ultra-fast Phenomena rElectron - hole recombinationsTimescale 30 fs - 200 fsInteraction times in liquidsTimescale 1ps - 100 psFast relaxations in large moleculesTimescale 30 fs - 200 fs

  • Femtosecond delay1 fs 0.3 mm7 fs 2 mm

  • Wave packets

    Wave- packet splitting at a Curve- crossingDiabatic states :12VInclude V in H0Adiabatic states :VNAEnergyrTIMERb2, D system heat- pipe ovenRb2, D;A system Effusive beamTOFCrossed supersonic- effusive beamsHe: cooling of Rb2Ar,Kr: Rb2 clusters

  • ExperimentalMode-locked fiber laserdelay- mirror/2 wave-plate+ prism compressorsfor both beams780 nm; 170 fs; 150 cm-1 Acetone inletPhoton countercomputerPump: 427nm, 5 J per pulse,1kHzProbe: 927nm, 2 J per pulse,1kHzPMtubeRb2Topas 1, OPATopas 2, OPA

  • Molecular quantum dynamics (MQD), Wavepacket (WP) and fs laser spectroscopy1. MQD nuclear vibration, rotation & change of electronic configuration. 2. WP nonstationary superposition of a set of wavefunctions with fixed phase relationship. 3. Pump-probe technique pump process, probe process, delay time and time zero.

  • Dynamics can be studied by Femtosecond spectroscopy ..Femtosecond laser:Pump laser, Er-doped fiber laser, kHz 2w YAG laserNon-linear setupsTOPAS: 270 nm ... 3 mmWLC generator: White light continuumMirrors, mirrors, ....

  • "3D Nozzle": Compressible Flow with Shock, Transition, Turbulence and Unsteadiness

    Wind tunnel at KTHp = ?H Alfredsson, N Tillmark, T Sigfrids, L-E

  • Pressure Sensitive Paint

    Method:Laser excitation of pressure sensitive paintin order to measure the gas pressure over a surface.

    Fluorescence measurementsLife-time measurementsLaser lightPressure sensitive paintFluorescence

  • Basic photophysicsPhoton transitions in an energy diagram of the condensed phaseS0S1S2SNT1Vibrationrelaxationshexcitationfluorescensinter system crossing ISCfosforescenstftp

  • Ruthenium based painttris(2,2-bipyridil) ruthenium Ru(bpy)

    300 400 500 600 700 wavelength (nm)IntensityAbsorption and emnission spectrumBinder: urethane, clear, is permeable to oxygenAr 4882w YAG3w YAG4w YAG

  • Pressure measurementsDecay - ratesQuenching = kq [L*] [O2]

    1/t[O2]Stern-Vollmer plot

  • InstrumentationPressure measurements on a surface with a jet nozzleMeasurements in the wind tunnel

    Frequency tripled YAG, Ar ion laser chopped, blue diod laserMechelle+ICCDor ICCD+filter

  • ICCD-camera

    ANDOR iStarDigital delay generatorPropagation delay 40 nsOptical gate width

  • MonochromatorResoving powerWavelength coverage190nm< l < 1.1mm3 m optical fibre

  • MechelleMechelle

  • Optical system

  • Pressure Sensitive Paint

  • PSP measurementsFrequency doubled YAG laser excitation Dt = 5ns, l = 532 nmlt0 = 4.0 (0.2) msl = 488 nm Ar ion











    Pressure /Torr)

    Invesre life-time (ms)

    PSP1 decay Stern-Vollmer plot



    Torr1/tarb. Scale











    Pressure /Torr)

    Invesre life-time (ms)

    PSP1 decay Stern-Vollmer plot



  • Time-resolved spectrum 340 350 wavelength

  • Time-resolved spectra cont.

  • Sonoluminiscence ShocktubesHigh pressureVacuumIntensePlanckRadiationM Lesser, N Apazidis H Alfredsson, N Tillmark, H Essn, Mechanics, L-E B

  • Experimental setup

  • Time-resolved spectra cont. lIT = ?

    Seminar 14-11-02 10.00 FA32


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