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Three lines of the fundamental rotation-vibration band of CN have been observed in the laboratory using a King furnace. The transition moment squared has been found to be .00075 plus or minus .00031 atomic units. In addition, the transition moment squared of the 0-0 band of the red system of CN has been measured to be 0.48 plus or minus 0.28 atomic units (an oscillator-strength of .00033 plus or minus .0019).
Experimental values for the visible vibration-dipole bands of HD are improved through a study of weak, unsaturated absorption lines of HD against a well-defined white light continuum at low gas densities between 0.3 and 1.7 amagats. Spectral resolution was high enough to allow recovery of line profiles with only minor corrections for instrumental effects, so line strengths and shapes are determined directly without recourse to theoretical assumptions regarding the curve of growth, and the unusual phenomenon of collision narrowing in HD is directly observed in the line shape for the first time. Accurate line strengths are reported, the behavior of spectral profiles as a function of gas density is discussed, and the pressure shift coefficients are determined. These are compared with previous laboratory work done either at lower spectral resolving power or at higher gas densities.
Photodissociation following absorption of extreme-ultraviolet photons is an important factor in determining the abundance and isotropic fractionation of CO in diffuse and translucent interstellar clouds. The principal channel for destruction of CO-13 in such clouds begins with absorption in the (1,0) vibrational band of the E1Pi - X1Sigma(+) system; similarly, absorption in the (0,0) band begins a significant destruction channel for CO-12. Reliable modeling of the CO fractionation process depends critically upon the accuracy of the photoabsorption cross section for these bands. We have measured the cross sections for the relevant isotropic species and for the (1,0) band of CO-12. Our results, which are uncertain by about 10 percent, are for the most part larger than previous measurements.
We report measured N2-broadening coefficients, gamma (T), of approximately 70 transitions of the ground electronic state fundamental vibration-rotation band (v=1 (left arrow) 0) of NO at 183, 213 and 296K. In addition to the broadening asymmetry previously observed between the 2 pi 3/2 and 2 pi 1/2 state transitions, we also observed for most of the 2 pi 1/2 transitions an increased broadening of the f-lambda over e-lambda components. The temperature dependence of the broadening coefficients was characterized by the power law, gamma T = gamma 296 (296/T) (sup n).
Attention is given to a far wing line shape theory based on binary collision and quasi-static approximations. The theory is applicable for both the LF and HF wings of vibrational-rotational bands. It is used to calculate the frequency and temperature dependence of the continuous absorption coefficient for frequencies up to 10,000/cm for pure water vapor. The results are compared with existing laboratory data in the 2400-2700/cm window and in the 3000-4300/cm band center region, with field measurements in the 2000-2225/cm region and with a recent experimental measurement near 9466/cm. It is concluded that both the magnitude and temperature dependence of the water vapor continuum can be accounted for by the present theory without the introduction of any adjustable parameters. Refinements of the theory and extension to foreign-broadened absorption are also discussed.
Methyl chloride (CH3Cl) is relatively abundant in the Earth's atmosphere, and because it is easily photodissociated is an important source of the chlorine atoms which are involved in the destruction of atmospheric ozone.
We present a narrow-band tracking control method using a variant of the Least Mean Squares (LMS) algorithm to isolate slowly changing periodic disturbances from engineering structures. The advantage of the algorithm is that it has a simple architecture and is relatively easy to implement while it can isolate disturbances on the order of 40-50 dB over decades of frequency band. We also present the results of an experiment conducted on a flexible truss structure. The average disturbance rejection achieved is over 40 dB over the frequency band of 5 Hz to 50 Hz.
Laboratory measurements of the v(3) band strength of HO2 using a tunable diode laser to measure the absorption strength of a vibration-rotation line in the P branch near 1080/cm are reported. The HO2 is generated in a discharge-flow system by reaction of fluorine atoms with excess H2O2: F + H2O2 - HO2 + HF. The HO2 concentration is determined from measurements of F-atom concentrations using both chemical titration with Cl2 and tunable diode laser absorption by the F-atom spin-orbit transition near 404/cm. The experimental data are consistent with a value of k(3) = (1.6 + or - 0.3) x 10 to the 12th cu cm/s and a ratio k(4)/k(1) = 1.0 + or - 0.4. The line strength for the 6(15) - 7(16)F(1) transition is 2.9 x 10 to the -21 sq cm/molecule/cm, which corresponds to a v(3) band strength of 35 + or - 9/sq cm/(STP atm). This value is a factor of 1.6 to 6 lower than previous ab initio calculations.
Laboratory tests of infrared spectrum of carbon suboxide, to determine presence in Venus and Mars atmospheres
P-branch laser oscillations have been observed in the v = 1 to v = 0 band of HF gas, optically pumped by R-branch lines of a pulsed HF laser. The observed gains are large (greater than 10% per cm), and the conversion efficiencies are high. In a ring cavity, the system shows directional gain anisotropy characteristic of unidirectional laser amplifiers proposed recently.
The HO2 radicals generated in a discharge-flow system were observed with tunable diode laser absorption in the P-branch of the nu(3) vibrationall band at 1080/cm. The observed line positions agree with those calculated from the molecular constants for the nu(3) bland obtained from a previous study using laser magnetic resonance spectroscopy. The band strength was determined by observing line center absoptions when HO2 is produced in the reaction F + H2O2 yields HO2 + HF (k1) with a measured concentration of atomic fluorine and excess hydrogen peroxide. F-atom concentrations are measured by diode laser absorption of the spin-orbit transition at 404/cm. The analysis accounts for HO2 losses due to the reactions of HO2 + HO2 yields H2O2 + O2 (k3) and F + HO2 yields HF + O2 (k4). The line strength for the 6(15) 7(16) F(1) transition is 2.9 x 10 to the 21st power sq cm/molecule/cm which corresponds to a nu(3) band strength of 34 +/- 9 sq/cm(STP atm). This value is a factor of 6 lower than previous ab initio calculations. These results will be useful in assessing the feasibility of atmospheric measurements of HO2 using infrared absorption techniques.
There is considerable interest in the kinetics and concentrations of free radicals in the stratosphere. Chlorine monoxide is a critically important radical because of its role in catalytic cycles for ozone depletion. Depletion occurs under a wide variety of conditions including the Antarctic spring when unusual mechanisms such as the BrO sub x/ClO sub x, ClO dimer (Cl sub 2 O sub 2), and ClO sub x/HO sub x cycles are suggested to operate. Infrared spectroscopy is one of the methods used to measure ClO in the stratosphere (Menzies 1979 and 1983; Mumma et al., 1983). To aid the quantification of such infrared measurements, researchers measured the ClO ground state fundamental band intensity.
The absolute intensity of the 4-0 vibration band of CO is measured in spectra obtained using a 25-m base-path multiple-traversal absorption cell and a 5-m scanning spectrometer. The intensities of individual vibration-rotation lines in this band are determined from measurements of their equivalent widths, and absolute values for the rotationless transition moment and the vibration-rotation interaction factor are derived from the measured line strengths. The experimentally obtained vibration-rotation function is compared with a theoretical curve; agreement between theory and experiment is found to be good for the P-branch but poor for the R-branch. It is noted that numerical solutions to the radial Schroedinger equation lead to vibration-rotation function values that are in good agreement with the experiment.
Wavelengths of rotational-vibrational hydroxyl bands
CO vibration-rotation bands, calculating high resolution and temperature steradiancy and spectral absorption coefficient
Material fatigue failure under narrow band random vibration effects, deriving fatigue life prediction equation based on composite experimental design and statistical tests
Intensity parameters for the vibration-rotation bands of ClO were calculated by evaluating matrix elements of the vibrational eigenfunctions using the theoretical dipole moment curve. These vibrational eigenfunctions are based on realistic Klein-Dunham potentials deduced from experimental values (Coxon et al, 1976) for certain vibrational energy levels. The data can be applied to the interpretation of remote or in situ experiments to deduce stratospheric ClO concentrations from vibration-rotation absorption spectra.
Relative intensities of the hydroxyl ion vibration-rotational bands