Relaxation of Molecules Exchanging Vibrational Energy

Rich, John Martin

doi:10.1016/b978-0-12-478803-9.50010-0

Cited by 24 publications

(21 citation statements)

References 102 publications

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“…The details of the actual distribution of energy among the vibrational quantum states is important in a more restricted range of problems, but is certainly key in non-thermal plasma chemical reactor design, in predicting radiation from supersonic nozzle expansions, and in the design of a variety of molecular gas lasers [3]. This energy distribution is primarily controlled by vibration-to-vibration (V-V) energy exchange processes [4,5],…”

Section: Introductionmentioning

confidence: 99%

Time-resolved Fourier-transform infrared spectroscopy of optically pumped carbon monoxide

Plönjes

Palm

Chernukho

et al. 1999

30th Plasmadynamic and Lasers Conference

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The paper discusses measurements of vibration-to-vibration (V-V) energy transfer rates for CO-CO using time-resolved step-scan Fourier transform infrared spectroscopy of optically pumped carbon monoxide. In the experiments, time evolution of all vibrational states of carbon monoxide excited by a CO laser and populated by V-V processes (up to v-40) is monitored simultaneously for the first time. The V-V rates are inferred from these data using a kinetic model that incorporates spatial power distribution of the focused laser beam, transport processes, and multi-quantum V-V processes. Although the model predictions agree well with the timedependent step-scan relaxation data, there is variance between the model predictions and the uppumping data, however. Comparison of calculations using two different sets of V-V rates with experimental spectra showed that the use of the semi-empirical V-V rates of DeLeon and Rich provides better agreement with experiment. It is also shown that the multi-quantum V-V rates among high vibrational quantum numbers, calculated by Cacciatore and Billing, are substantially overpredicted. The results provide some new insight into nonequilibrium vibrational kinetics, ' and also demonstrate the capabilities of the step-scan Fourier transform spectroscopy for timeresolved studies of molecular energy transfer processes and validation of theoretical rate models.

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Section: Introductionmentioning

confidence: 99%

Time-resolved Fourier-transform infrared spectroscopy of optically pumped carbon monoxide

Plönjes

Palm

Chernukho

et al. 1999

30th Plasmadynamic and Lasers Conference

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“…While the total number of vibrational quanta will indeed be approximately equal to that corresponding to a frozen vibrational temperature, the distribution could be much different, with molecules in V 00 1 transferred to higher V 00 levels [40]. LRS signals in 15M6 at 700 K stagnation temperature transition from molecular to clustered levels as stagnation pressure increases from 0.345-2.07 MPa (50-300 psi).…”

Section: Discussionmentioning

confidence: 99%

Rayleigh Scattering Density Measurements, Cluster Theory, and Nucleation Calculations at Mach 10

Balla

Everhart

2012

AIAA Journal

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In an exploratory investigation, quantitative unclustered laser Rayleigh scattering measurements of density were performed in the air in the NASA Langley Research Center's 31 in. Mach 10 wind tunnel. A review of 20 previous years of data in supersonic and Mach 6 hypersonic flows is presented where clustered signals typically overwhelmed molecular signals. A review of nucleation theory and accompanying nucleation calculations are also provided to interpret the current observed lack of clustering. Data were acquired at a fixed stagnation temperature near 990 K at five stagnation pressures spanning 2.41 to 10.0 MPa (350 to 1454 psi) using a pulsed argon fluoride excimer laser and double-intensified charge-coupled device camera. Data averaged over 371 images and 210 pixels along a 36.7 mm line measured freestream densities that agree with computed isentropic-expansion densities to less than 2% and less than 6% at the highest and lowest densities, respectively. Cluster-free Mach 10 results are compared with previous clustered Mach 6 and condensation-free Mach 14 results. Evidence is presented indicating vibrationally excited oxygen and nitrogen molecules are absorbed as the clusters form, release their excess energy, and inhibit or possibly reverse the clustering process. Implications for delaying clustering and condensation onset in hypersonic and hypervelocity facilities are discussed.

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“…(7) to create a true discharge in the optically pumped cell, a discharge that is unconditionally stable, avoiding glow-to-arc collapse. This is demonstrated by placing RF electrodes about the optically pumped plasma in the cell of Fig.…”

Section: Optically Pumped Cool Electric Dischargesmentioning

confidence: 99%

“…Free electrons are produced by associative ionization processes from the excited gases, in collisions of two highly vibrationally excited molecules, AB(v) + AB(w) -+ (AB) + e (7) E+E >E10…”

Section: Optically Pumped Cool Electric Dischargesmentioning

confidence: 99%

“…it must be emphasized that the results shown in Figs. [5][6][7] were obtained with a CO partial pressure of 50 Ton. Nevertheless, the nonequilibrium vibrational up-pumping necessary to drive the nanotube synthesis process also has been demonstrated to occur at CO pressures in excess of one atmosphere'9.…”

Section: Single-walled Carbon Nanotube Synthesis In Optical Dischargesmentioning

confidence: 99%

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High-power CO lasers and some recent applications

et al. 2002

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The electric-discharge-excited carbon monoxide laser is one of the most efficient laser sources known that is scalable to very high continuous wave powers. We review work at Ohio State where such lasers are used to excite flowing molecular gas plasmas, in mixtures of CO and other diatomic gases, including air. These plasmas are stable, diffuse, and can be operated at high gas pressures and low gas kinetic temperature. They are being employed for various plasma chemistry applications. Recent results are presented in which such an "optically pumped" plasma reactor is used to synthesize single-walled carbon nanotubes, which show surprising order and alignment 1NFRODUCTIONThe electrically-excited carbon monoxide (CO) gas laser, operating on the CO fundamental infrared band around 5It wavelength, remains one of the most efficient high power lasers that is scalable to very high c.w. outputs. CO lasers have a demonstrated thermal conversion efficiency, electrical power in to broadband laser output, of flth 50% '. Systems have been built with c.w. or average powers in the MW range?'3. Despite these impressive performance levels, CO lasers have not been widely employed in industrial applications, and are still rather uncommon even in the research laboratory. The most important cause of this neglect is undoubtedly the need for operation at cryogenic gas temperatures to achieve the highest efficiency. The bestperforming systems have gas temperatures of -425K. Even if the necessary cooling of the system is charged against performance, the overall efficiency ofa closed cycle system can be a respectable 3Ø%4, still a leader among gas lasers. The systems complications of providing the requisite degree of cooling, however, with the consequent capital and operational costs, commonly act against the laser being the system of choice.Further drawbacks include the well-known feature that the laser output at the highest powers and efficiency is obtained when operating the system as a broadband oscillator. In this case, the output is strongly multi-line, being distributed over some tens ofvibration-rotation spectral lines range from -4.7 to 5.7 t wavelength. Further, some of these lines are strongly absorbed by water vapor, degrading performance in applications involving transmission through moist atmospheres. Intense work, continuing in recent years, led by the Gas Laser Laboratory at the Lebedev Institute in Moscow and Air Force Research Laboratory at Kirtland AFB, has led to considerable mitigation of these problems. CO lasers are being developed with good single line, or restricted wavelength multiline, performance on both the CO fundamental band and the first overtone band at 2.5However, performance is still below the broadband levels, and such line selection operation has its own systems complications.Notwithstanding these difficulties, the high power and efficiency of CO lasers at mid-IR wavelengths make them intriguing sources for certain advanced processing applications. Such applications involve using the laser to create larg...

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Relaxation of Molecules Exchanging Vibrational Energy

Cited by 24 publications

References 102 publications

Time-resolved Fourier-transform infrared spectroscopy of optically pumped carbon monoxide

Time-resolved Fourier-transform infrared spectroscopy of optically pumped carbon monoxide

Rayleigh Scattering Density Measurements, Cluster Theory, and Nucleation Calculations at Mach 10

High-power CO lasers and some recent applications

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