The effect of laser linewidth on two-photon absorption rates

Marx, B. R.; Simons, J. K.; Allen, L.

doi:10.1088/0022-3700/11/8/004

Cited by 48 publications

(8 citation statements)

References 6 publications

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“…The basic procedure for extracting translational temperature from observed lineshape for two-photon transitions is described by Marx and Allen [11]. The width of the resulting spectrum in absolute frequency is given by the following expression:…”

Section: Translational Temperaturesmentioning

confidence: 99%

Arc Wind Tunnel Flow Characterization Measured by Laser-Induced Fluorescence of Atomic Species

Takayanagi

Mizuno

Fujii

et al. 2009

41st AIAA Thermophysics Conference

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Two-photon Laser induced fluorescence for atomic nitrogen is applied to the 750kW arc heated wind tunnel in JAXA in order to obtain the number density of atomic nitrogen. A flow reactor is installed in order to calibrate the number densities of atomic nitrogen. With the titration method of nitric oxide, the number density of atomic nitrogen in the flow reactor was estimated as 1.3 x 10 21 m -3 . As a result, the number density of atomic nitrogen in the arc heated wind tunnel flow was estimated from to . These values are same order of magnitude comparing with simulated ones. Nomenclature a = effective branching ratio of the observed fluorescence transition A p = cross sectional area of laser beam c = velocity of light, m/s E p = laser pulse energy, J F(t) = normalized temporal profile of laser pulse h = Planck's constant, J s I = electric current, A K L = laser calibration constant K = spectroscopic calibration constant K = geometric calibration constant k B = Boltzmann constant, 1.38 x 10 -23 J/K m = mass flow rate, kg/s M A = atomic mass, kg N A = Avogadro's constant N 1 = number density of atomic nitrogen, m -3 N tot = total gas number density, m -3 p = pressure, Pa R = gas constant, J/K mol S = spectrally integrated fluorescence signal T = transmittance of optics T tr = translational temperature, K v = velocity of flow, m/s V = volume of imaged region, m 3 = quantum yield = flow rate of the titration gas, sccm tot = total gas flow rate, sccm = detector spectral efficiency and gain 0 = center excitation wavelength, nm D = Doppler width, nm e = full width at half maximum in the excitation profile, nm laser = laser line width, nm = two photon absorption cross section 12 (2) = two photon absorption cross section L = laser frequency, Hz = formed angle of the path along the stagnation stream line and fluorescence light path, degree r = collection optics solid angle, sr

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Section: Translational Temperaturesmentioning

confidence: 99%

Arc Wind Tunnel Flow Characterization Measured by Laser-Induced Fluorescence of Atomic Species

Takayanagi

Mizuno

Fujii

et al. 2009

41st AIAA Thermophysics Conference

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“…The laser profile of the system used in this campaign is dominated by a Lorentz shape [33], which complicates the accurate identification of the line broadening. Here, the analytical method as described by Marx et al [34] or Grinstead et al [35] cannot be used because the measured line profile of the atomic transition is a Voigt function, i.e., the convolution of a Gaussian with a Lorentzian function [36][37][38]. The Gaussian part covers the broadening due to the kinetic temperature and the Lorentzian part (instrumental broadening) is believed to be due to the few cycles in the laser dye resonator within the short time of 4.9 ns [33].…”

Section: S D a 21mentioning

confidence: 99%

Two-Photon Absorption Laser-Induced Fluorescence Investigation of CO2 Plasmas for Mars Entry

Marynowski

Löhle

Fasoulas

2014

Journal of Thermophysics and Heat Transfer

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Two-photon absorption laser-induced fluorescence measurements have been conducted to investigate atomic oxygen temperature and number density in a CO 2 plasma relevant to Martian entry. The high-enthalpy plasma flow has been produced by an inductively heated plasma generator. This paper describes the experimental setup and shows the applicability of laser diagnostics to Mars-relevant plasmas. Particular emphasis is put on the use of the generated data for the numerical simulation of the aerothermal chemistry of a Martian entry. Relative fluorescence signals are calibrated by a procedure using xenon as a reference. This calibration method allows the in situ experimental determination of the instrumental broadening of the spectroscopic setup and thus an accurate temperature measurement. The acquired, highly resolved line profiles of the fluorescence signal yield a translational temperature of 2777 K 400 K and a mean number density of 1.55 · 10 19 m −3 60%. Nomenclature= molar mass of oxygen _ m CO 2 = CO 2 mass flow n = number density N A = Avogadro constant P el = electrical power p amb = ambient tank pressure Q = quenching coefficient S = fluorescence signal T tr = translational temperature U = voltage η = transmissivity and quantum efficiency factor λ = wavelength σ 2 = absorption cross section

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“…13) Some researchers made additional measurements in order to convert the integral signal values to absolute atom number density by quantification of the temporal and spatial characteristics of the laser pulse and the signal collection efficiency, and measured values of the absolute two-photon excitation cross section for the transition and of the second-order coherence factor for the laser used in these experiments.…”

Section: Theorymentioning

confidence: 99%

Application of Two-Photon Absorption Laser-Induced Fluorescence to Atomic Species in the JAXA 750 kW Arc-Heated Wind Tunnel

Takayanagi

Mizuno

Fujii

et al. 2014

Trans. Japan Soc. Aero. S Sci.

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Two-photon absorption laser induced fluorescence (TALIF) is applied to atomic oxygen and nitrogen generated in the JAXA 750 kW arc-heated wind tunnel in order to obtain velocity, translational temperature and atomic number density distributions. Free stream velocity is estimated by Doppler shift and the translational temperature distributions are deduced from spectral broadening. The absolute center excitation wavelength and laser line width are estimated with the TALIF profiles from a static reference cell which is called as a flow reactor. In this flow reactor, atomic species are generated by microwave discharge. The spatial distributions of atomic number density are deduced from the integrated TALIF profiles. The absolute atomic number densities inside the flow reactor are estimated with a titration method. From the mass fraction estimation, it is found that the number densities of atomic oxygen are overestimated owing to the saturation effect. When oxygen is assumed to be totally dissociated, the fractional enthalpies are estimated.

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The effect of laser linewidth on two-photon absorption rates

Cited by 48 publications

References 6 publications

Arc Wind Tunnel Flow Characterization Measured by Laser-Induced Fluorescence of Atomic Species

Arc Wind Tunnel Flow Characterization Measured by Laser-Induced Fluorescence of Atomic Species

Two-Photon Absorption Laser-Induced Fluorescence Investigation of CO2 Plasmas for Mars Entry

Application of Two-Photon Absorption Laser-Induced Fluorescence to Atomic Species in the JAXA 750 kW Arc-Heated Wind Tunnel

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