Rotational relaxation in a line-selected continuous HF chemical laser

Skifstad, J. G.; Chao, C. M.

doi:10.1364/ao.14.001713

Cited by 16 publications

(2 citation statements)

References 6 publications

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“…Rotational energy transfer ͑RET͒ rates influence many fundamental processes such as sound propagation, absorption, and dispersion in a gas medium, 1-4 the population evolution of nonequilibrium systems like the high temperature environment of flames, 4,5 the viscosity of a gas, 4 optical pumping processes, [6][7][8][9][10][11] and the pressure broadening of spectral linewidths. [12][13][14] Data for RET processes are needed to predict and explain the final quantum state populations of exothermic reactions [15][16][17] and chemical lasers.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the state-to-state rotational relaxation rate constants for carbon monoxide (CO) using infrared double resonance

Phipps

Smith

Hager

et al. 2002

The Journal of Chemical Physics

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information , 1215 Jefferson Davis Highway. Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 0MB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air Force Research Laboratory/Directed Energy Directorate,Kirtland Air Force Base, New Mexico 87117-5776 SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution is unlimited State-to-state rotational relaxation of carbon monoxide (CO) has been studied using an IR double resonance technique. Individual rotational lines of the (2-0) vibrational overtone band were pumped by a pulsed tunable IR laser and the subsequent evolution of the v=2 rotational population distribution was monitored by the absorption of a tunable cw IR laser via the (3-2) band transitions. Both the excitation and probe lasers were linearly polarized, with linewidths that were narrower than the CO Doppler width. Consequently, alignment and velocity relaxation effects were observed in these measurements. A data set consisting of 54 time-dependent rotational state population profiles was acquired. The full CO-CO rotational relaxation matrix, which consists of state-to-state rate constants for rotational levels up to J = 29, was deduced from computer simulations of the data. Scaling and fitting laws were used to provide parametric representations of the rate constants. The three most common models, modified exponential gap (MEG), statistical polynomialexponential gap (SPEG), and energy corrected sudden with exponential-power gap (ECS-EP) were investigated. We concluded that the SPEG law best reproduced the CO-CO rotational energy transfer data. A propensity to preserve the CO parity in rotational energy transfer was observed for collisions where the amount of energy transferred was small. Hence, even AJ processes were favored for transitions between levels with low I values. For nearsingle collision events a correlation was noted between the amount of rotational energy transferred and the degree of velocity distribution relaxation. This correlation yielded insights regarding the energy transfer dynamics. State-to-state rotational relaxation of carbon monoxide (CO) has been studied using an ir double resonance technique. ...

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Section: Introductionmentioning

confidence: 99%

Investigation of the state-to-state rotational relaxation rate constants for carbon monoxide (CO) using infrared double resonance

Phipps

Smith

Hager

et al. 2002

The Journal of Chemical Physics

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“…For example, it has been postulated that if the spatial optical modes of the laser do not fill the entire gain volume or if the HF laser medium is inhomogeneous (i.e., the laser has a non-uniform flow field), multi-line output could resuh. However, according to the HF laser modeling community, only models that include rotational nonequilibrium are able to reproduce multiline lasing (Cohen et al 1986;Sentman 1975;Sentman et al 1989a;Sentman et al 1984;Skifstad and Chao 1975). In addition, models that allow rotational nonequilibrium are more successful at predicting HF laser performance than those that assume rotational equilibrium (Cohen et al 1986;Sentman 1975).…”

Section: Saturated Gainmentioning

confidence: 99%

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

et al. 2004

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Public reporting burden for this collection of information te Bstimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information. The overtone gain of a small-scale HF laser was measured using a sub-Doppler tunable diode laser system. Two-dimensional spatially resolved small signal gain and temperature maps were generated, which show a highly inhomogeneous gain medium indicating the dominant role that mixing of the fuel and oxidizer streams has in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics code. To reduce uncertainty of important modeling input parameters, novel measurements of reactant concentration, flow velocity and gain length were made. Results show that reactant mixing mechanisms such as turbulence and large-scale vortex structures have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms such as reaction rate constants and reactant concentration have a greater effect on the maximum system gain. Overtone gain data measured while operating the laser saturated on the fundamental transitions are compared with fundamental lasing output spectra. In all cases, the data are consistent with an equilibrium rotational distribution.

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Laser dynamics and rotational relaxation in chemically formed carbon monoxide

Darée

Hesse

1976

Optics Communications

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Rotational relaxation in a line-selected continuous HF chemical laser

Cited by 16 publications

References 6 publications

Investigation of the state-to-state rotational relaxation rate constants for carbon monoxide (CO) using infrared double resonance

Investigation of the state-to-state rotational relaxation rate constants for carbon monoxide (CO) using infrared double resonance

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

Laser dynamics and rotational relaxation in chemically formed carbon monoxide

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