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1

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Quenching and vibrational energy transfer in the B 2Π state of the NS molecule (1989)

Wysong, Ingrid J. ; Jeffries, Jay B. ; Crosley, David R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 91 (1989), S. 5343-5351

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Quenching and vibrational energy transfer in the B2Π state of the NS free radical have been studied using temporally and spectrally resolved laser-induced fluorescence in a low-pressure discharge flow reactor. The collision partners were He, Ar, H2, N2, O2, SF6, CO2, and N2O. Total removal cross sections show an oscillatory behavior with v' in the range of unperturbed levels, v'=4–7, for all colliders studied save O2 where a nearly monotonic increase is seen. Vibrational transfer occurs for H2 and the polyatomics; the rates vary little with v'. Δv=2 transfer occurs with the polyatomic colliders for v'=5. Fluorescence decay traces from the perturbed v'=3 and 8 levels differ from the unperturbed levels and from each other. v'=3 is perturbed by quartets and shows "gateway'' level behavior whereas v'=8 is perturbed by a doublet and shows efficient interelectronic transfer for all rotational levels.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.457665

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2

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Rotational level dependence of the electronic quenching of NH2A˜ by helium (1990)

Wysong, Ingrid J. ; Jeffries, Jay B. ; Crosley, David R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 93 (1990), S. 237-241

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The rotational level dependence of the electronic quenching of the A˜2A1 state of the NH2 radical is investigated by time-resolved laser-induced fluorescence. Quenching of ∑(0,9,0) is found to increase monotonically with rotational level from 2×10−11 cm3s−1 for N'=0 to 7×10−11 cm3 s−1 for N'=7. Measurements on the neighboring ∑(0,7,0), Π(0,8,0), and Π(0,10,0) vibronic levels show no significant rotational level dependence. The behavior in ∑(0,9,0) cannot be satisfactorily explained by either molecular collision dynamics or by state mixing.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.459597

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3

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Parity propensities in rotational energy transfer of OH X 2Πi with helium (1991)

Wysong, Ingrid J. ; Jeffries, Jay B. ; Crosley, David R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 94 (1991), S. 7547-7549

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Rotational energy transfer in OH (X 2Πi, v=2) induced by collisions with He, has been studied using a two-laser technique. Strong propensities are found for conservation of total parity in collisions which change the rotational level and spin orbit component. These results have implications concerning the shape of the OH–He potential.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.460187

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4

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Quenching of A 2Σ+ OH at 300 K by several colliders (1990)

Wysong, Ingrid J. ; Jeffries, Jay B. ; Crosley, David R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 92 (1990), S. 5218-5222

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Collisional quenching of the v'=0 level of the A 2Σ+ state of the OH molecule has been studied for a variety of collision partners. The pressure dependence of time-resolved, laser-induced fluorescence furnishes the quenching cross sections σQ. OH radicals are produced in a microwave discharge or by photolysis of HNO3 at 193 nm, always in sufficient Ar bath to produce a thermal rotational population at 300K in the laser-excited A 2Σ+ state. For Kr and Xe, the σQ are 8 and 27 A(ring) 2, respectively; comparison with a prior study suggests a decrease in σQ with increasing rotational level and/or increasing temperature. σQ (O2)=18 A(ring) 2,and σQ (H2O)=80 A(ring) 2; cross sections were measured for selected freons and butanes also important in tropospheric laser measurements of OH.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.458558

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5

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Vibrational energy transfer of NO (X 2Π, v=2 and 1) (1994)

Wysong, Ingrid J.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 101 (1994), S. 2800-2810

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: A two-laser (ir overtone pump and uv laser-induced fluorescence probe) technique has been used to measure vibrational relaxation rate coefficients for NO (X 2Π, v=2 and 1) with various collision partners at room temperature. The relaxation of v=2 by NO, H2, and NH3 has also been measured at 240 K. The relaxation of v=2 by NO is dominated by vibration-to-vibration (V–V) transfer and this process has not previously been measured below room temperature. The probability for V–V transfer increases with decreasing temperature, indicating that attractive forces play a key role in this process. Different physical mechanisms for NO vibrational energy transfer are discussed in light of the available data.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.467595

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Vibrational favoring effect in DSMC dissociation models (1997)

Wadsworth, Dean C. ; Wysong, Ingrid J.

[S.l.] : American Institute of Physics (AIP)

Physics of Fluids 9 (1997), S. 3873-3884

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ISSN: 1089-7666

Source: AIP Digital Archive

Topics: Physics

Notes: Several common models for dissociation reactions in direct simulation Monte Carlo calculations are analyzed quantitatively under general equilibrium and nonequilibrium conditions. The models differ in the degree to which the internal energy of the colliding particles contributes to the probability of dissociation. Test calculations in an equilibrium bath show that the temperature dependence of the predicted equilibrium rate constant, a commonly used measure of accuracy, is dominated by the collision selection algorithm, rather than the details of the dissociation model, and is thus a poor measure of physical validity or accuracy. The distribution of internal energy states of molecules selected for dissociation under the bath conditions, as used for analysis here, is a preferred means to assess accuracy, and is available qualitatively from existing theory. Recent state-specific quasi-classical trajectory calculations allow for quantitative assessment for certain molecules. Certain singularities present in a recent threshold dissociation model [Phys. Fluids 8, 1293 (1996)] are mediated by recourse to the full threshold equations. Sensitivity studies are performed to show the effect of the details of the numerical implementation. A simple generalization of a Weak Vibrational Bias model [Phys. Fluids 6, 3473 (1994)] is suggested to include rotational favoring. The present analysis provides a means to generate quantitatively a two-temperature rate constant, commonly applied in continuum models, for arbitrary conditions. Calibrated simulations which differ only in the dissociation model are performed for the hypersonic stagnation streamline problem to confirm the order of magnitude decrease in dissociation relative to a standard nonfavored model under conditions of large nonequilibrium. © 1997 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.869487

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7

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Assessment of direct simulation Monte Carlo phenomenological rotational relaxation models (1998)

Wysong, Ingrid J. ; Wadsworth, Dean C.

[S.l.] : American Institute of Physics (AIP)

Physics of Fluids 10 (1998), S. 2983-2994

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ISSN: 1089-7666

Source: AIP Digital Archive

Topics: Physics

Notes: We address direct simulation Monte Carlo (DSMC) implementation of phenomenological models of the rotational relaxation process suitable for an arbitrary gas mixture composed of atomic and quantized diatomic species. The macroscopic relaxation process is parametrized by a constant or temperature-dependent collision number Zr such as that of Parker [Phys. Fluids 2, 449 (1959)]. The energy redistribution properties predicted by such a model at the collision level are compared with a recent quasiclassical state-to-state model. Modified forms of the constant collision number, and thus constant relaxation probability, serial quantized Borgnakke–Larsen algorithm [Phys. Fluids A 5, 2278 (1993)] and the null collision SICS-D algorithm [Phys. Fluids A 4, 1782 (1992)] are shown to be equivalent. The generalization to an energy-dependent relaxation probability [Phys. Fluids 6, 4042 (1994)] leads to a systematic bias toward delayed relaxation, due to approximations inherent in the analytical formulation. The error induced in the predicted relaxation behavior as a function of temperature is approximately equivalent in magnitude to a previously proposed, but unrelated, correction factor [Phys. Fluids 6, 2191 (1994)], and also to the variation in the temperature-dependent Parker collision number over a wide range of conditions. Comparisons between DSMC and state-to-state calculations of the rotational distribution function in a relaxing bath quantify the microscopic limitations of the phenomenological model. Finally, a direct comparison of DSMC results with experimental shock layer measurements demonstrates that the energy-dependent relaxation model has a negligible advantage over the constant probability model when the collision number is chosen judiciously. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.869818

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