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Journal ArticleDOI

Two-photon cross-section calculations for krypton in the 190–220 nm range

01 Dec 2020-Applied Optics (Optical Society of America)-Vol. 59, Iss: 34, pp 10826-10837
TL;DR: It is concluded that two-photon excitation at 212.556 nm is optimal for single-laser, krypton tagging velocimetry or krypt on planar laser-induced fluorescence, which provides fundamental physical understanding of the Kr atom.
Abstract: This paper presents multi-path, two-photon excitation cross-section calculations for krypton, using first-order perturbation theory. For evaluation of the two-photon-transition matrix element, this paper formulates the two-photon cross-section calculation as a matrix mechanics problem. From a finite basis of states, consisting of 4p, 5s, 6s, 7s, 5p, 6p, 4d, 5d, and 6d orbitals, electric dipole matrix elements are constructed, and a Green’s function is expressed as a truncated, spectral expansion of solutions, satisfying the Schrodinger equation. Electric dipole matrix elements are evaluated via tabulated oscillator strengths, and where those are unavailable, quantum-defect theory is used. The relative magnitudes of two-photon cross-sections for eight krypton lines in the 190–220 nm range are compared to experimental excitation spectra with good agreement. This work provides fundamental physical understanding of the Kr atom, which adds to experimental observations of relative fluorescence intensity. This is valuable when comparing excitation schemes in different environments for krypton fluorescence experiments. We conclude that two-photon excitation at 212.556 nm is optimal for single-laser, krypton tagging velocimetry or krypton planar laser-induced fluorescence.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors apply Krypton Tagging velocimetry (KTV) to measure velocity profiles in the freestream of a large, national-scale high-enthalpy facility, the T5 Reflected-Shock Tunnel at Caltech.
Abstract: We apply Krypton Tagging Velocimetry (KTV) to measure velocity profiles in the freestream of a large, national-scale high-enthalpy facility, the T5 Reflected-Shock Tunnel at Caltech. The KTV scheme utilizes two-photon excitation at 216.67 nm with a pulsed dye laser, followed by re-excitation at 769.45 nm with a continuous laser diode. Results from a nine-shot experimental campaign are presented where N $$_2$$ and air gas mixtures are doped with krypton, denoted as 99% N $$_2$$ /1% Kr, and 75% N $$_2$$ /20% O $$_2$$ /5% Kr, respectively. Flow conditions were varied through much of the T5 parameter space (reservoir enthalpy $$h_R\approx 5-16$$ MJ/kg). We compare our experimental freestream velocity-profile measurements to reacting, Navier–Stokes nozzle calculations with success, to within the uncertainty of the experiment. Then, we discuss some of the limitations of the present measurement technique, including quenching effects and flow luminosity; and, we present an uncertainty estimate in the freestream velocity computations that arise from the experimentally derived inputs to the code.

8 citations

Proceedings ArticleDOI
03 Jan 2022
TL;DR: Krypton Tagging Velocimetry (KTV) and Picosecond Laser Electronic Excitation Tagging (PLEET) at a 100-kHz rate were demonstrated in Mach 18 flow conditions at the Arnold Engineering Development Center (AEDC) Tunnel 9 employing a burstmode laser system and a custom optical parametric oscillator (OPO) as discussed by the authors .
Abstract: Krypton Tagging Velocimetry (KTV) and Picosecond Laser Electronic Excitation Tagging (PLEET) velocimetry at a 100-kHz rate were demonstrated in Mach 18 flow conditions at the Arnold Engineering Development Center (AEDC) Tunnel 9 employing a burst-mode laser system and a custom optical parametric oscillator (OPO). The measured freestream flow velocities from both KTV and PLEET agreed well with the theoretical calculation. The increase in repetition rate provides better capability to perform time-resolved velocimetry measurements in hypersonicflowenvironments.

6 citations

Journal ArticleDOI
TL;DR: Krypton Tagging Velocimetry (KTV) and Picosecond Laser Electronic Excitation Tagging (PLEET) were demonstrated in Mach 18 flow conditions at the Arnold Engineering Development Center (AEDC) Tunnel 9 employing a burstmode laser system and a custom optical parametric oscillator (OPO) as discussed by the authors .
Abstract: Krypton Tagging Velocimetry (KTV) and Picosecond Laser Electronic Excitation Tagging (PLEET) velocimetry at a 100-kHz rate were demonstrated in Mach 18 flow conditions at the Arnold Engineering Development Center (AEDC) Tunnel 9 employing a burst-mode laser system and a custom optical parametric oscillator (OPO). The measured freestream flow velocities from both KTV and PLEET agreed well with the theoretical calculation. The increase in repetition rate provides better capability to perform time-resolved velocimetry measurements in hypersonic flow environments.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the application of a picosecond TALIF technique in krypton (Kr) at variable pressure (0.1-10 mbar) is investigated, where the laser intensity (I, units this http URL$^{-2}$) is tuned between 1 and 480.
Abstract: The present study focuses on the application of a picosecond (ps) TALIF technique in krypton (Kr) at variable pressure (0.1-10 mbar). The laser intensity (I, units this http URL$^{-2}$) is tuned between 1 and 480 this http URL$^{-2}$, and the depletion of the density of the Kr 5p'[3/2]$_2$ fluorescing state through photoionization (PIN) and amplified stimulated emission (ASE) is investigated. This is done by combining TALIF experiments with a simple 0D numerical model. We demonstrate that for a gas pressure of 3 mbar and 15 < $\le$ 480 this http URL$^{-2}$, a saturated fluorescence signal is obtained, which is largely attributed to PIN, ASE being negligible. Also, a broadening of the two-photon absorption line (i.e. 4p$^6$ $^1$S0$\to$5p'[3/2]$_2$) is recorded due to the production of charged species through PIN, inducing a Stark effect. For I$\le$15 this http URL$^{-2}$, though, PIN is significantly limited, the absorption line is noticeably narrowed, and the quadratic dependence of the TALIF signal intensity versus the laser energy is obtained. Thus, in this case, the investigated Kr TALIF scheme, using the 5p'[3/2]$_2\to$5s[3/2]$_1$ fluorescence channel, can be used for calibration purposes in ps-TALIF experiments. These results are of interest for fundamental research since most ps-TALIF studies performed in Kr do not investigate in detail the role of PIN and ASE on the depletion of the Kr 5p'[3/2]$_2$ state density. Moreover, this work contributes to the development of ps-TALIF for determining absolute densities and quenching coefficients of H and N atoms in plasmas. This is useful in numerous plasma-based applications (e.g. thin film synthesis, biomedical treatments, plasma-assisted combustion, ...), for which the knowledge of the density/kinetics of reactive atoms is essential.

2 citations

References
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Book
Chul Park1
01 Jan 1989
TL;DR: In this paper, nonequilibrium phenomena in hypersonic flows are examined on the basis of theoretical models and selected experimental data, in an introduction intended for second-year graduate students of aerospace engineering.
Abstract: Nonequilibrium phenomena in hypersonic flows are examined on the basis of theoretical models and selected experimental data, in an introduction intended for second-year graduate students of aerospace engineering. Chapters are devoted to the physical nature of gas atoms and molecules, transitions of internal states, the formulation of the master equation of aerothermodynamics, the conservation equations, chemical reactions in CFD, the behavior of air flows in nonequilibrium, experimental aspects of nonequilibrium flow, a review of experimental results, and gas-solid interaction. Diagrams, graphs, and tables of numerical data are provided.

1,331 citations


"Two-photon cross-section calculatio..." refers methods in this paper

  • ...Per Park [39], the 〈r 〉 is proportional to the Debeye length dD:...

    [...]

  • ...Per Park [39], the 〈r 〉 is proportional to the Debeye length dD: nmax = √ Ze dD 10ao ≈ Z2e εo kb e 2 ( Ne Te V + Ne TV ) (10ao )2 14 , (13) where Ne/V is the electron number density, Ni/V is the ion number density, Te is the electron temperature, and Ti is the Kr ion temperature....

    [...]

Journal ArticleDOI
TL;DR: The objective of this article is to continue where a previous review of TD-DFT in Volume 55 of the Annual Review of Physical Chemistry left off and highlight some of the problems and solutions from the point of view of applied physical chemistry.
Abstract: The classic density-functional theory (DFT) formalism introduced by Hohenberg, Kohn, and Sham in the mid-1960s is based on the idea that the complicated N-electron wave function can be replaced with the mathematically simpler 1-electron charge density in electronic structure calculations of the ground stationary state. As such, ordinary DFT cannot treat time-dependent (TD) problems nor describe excited electronic states. In 1984, Runge and Gross proved a theorem making TD-DFT formally exact. Information about electronic excited states may be obtained from this theory through the linear response (LR) theory formalism. Beginning in the mid-1990s, LR-TD-DFT became increasingly popular for calculating absorption and other spectra of medium- and large-sized molecules. Its ease of use and relatively good accuracy has now brought LR-TD-DFT to the forefront for this type of application. As the number and the diversity of applications of TD-DFT have grown, so too has our understanding of the strengths and weakness...

683 citations

Journal ArticleDOI
TL;DR: In this article, the relationships among various parameters describing the strength of optical transitions in atoms and molecules are reviewed and the application of these parameters to the description of the interaction between nearly monochromatic, directional light beams and atoms and molecule is given careful attention.
Abstract: The relationships among various parameters describing the strength of optical transitions in atoms and molecules are reviewed. The application of these parameters to the description of the interaction between nearly monochromatic, directional light beams and atoms and molecules is given careful attention. Common pitfalls in relating these parameters are pointed out.

600 citations

Posted Content
TL;DR: In this paper, the relationships among various parameters describing the strength of optical transitions in atoms and molecules are reviewed, and the application of these parameters to the description of the interaction between nearly monochromatic, directional light beams and atoms and molecular molecules is given careful attention.
Abstract: The relationships among various parameters describing the strength of optical transitions in atoms and molecules are reviewed. The application of these parameters to the description of the interaction between nearly monochromatic, directional light beams and atoms and molecules is given careful attention. Common pitfalls in relating these parameters are pointed out. This is a revised (February, 2002) version of a paper that originally appeared in Am. J. Phys. 50, 982-986 (1982).

510 citations

Book ChapterDOI
01 Jan 1996
TL;DR: In this article, a review of the state of the art in spatially and temporally precise laser diagnostics for temperature and species is presented, including two-dimensional implementations, their state of maturity assessed, and major remaining research issues identified.
Abstract: Nonintrusive laser probing of unsteady combustion processes provides the capability for the remote, in—situ, spatially and temporally precise measurement of, among other parameters, gas temperature and species concentrations. The predominant spatially—precise laser diagnostics for temperature and species include spontaneous Raman scattering (RS) and coherent anti-Stokes Raman spectroscopy (CARS) for measurements of major, i.e., ≥~ 1%, constituents, and laser—induced fluorescence spectroscopy (LIFS) and degenerate four wave mixing (DFWM) for minor, ppm level, species. Rayleigh scattering can provide total density measurements. These techniques are reviewed, including two-dimensional implementations, their state of maturity assessed, and major remaining research issues identified.

472 citations