Positive System Of CO Research Articles

Crosstalk-Free Excitation Scheme for Quantitative OH Laser-Induced Fluorescence in Environments Containing Excited CO

Spectral overlap in the single-photon laser-induced fluorescence between the 3064 Å system of OH and the third positive system of CO is detected in a highly-excited environment, namely, a CO2-H2O plasma. The overlap is distorting excitation and fluorescence spectra as well as fluorescence time decays of commonly used excitation transitions of OH. As a consequence, systematic errors are introduced into the determination of temperatures, gas compositions, and absolute number densities. The P1(2) transition is proposed to circumvent the distortion while still allowing for quantitative measurements due to the availability of non-radiative rate coefficients.

Dynamics of radiation in a CO:N2 mixture behind strong shock waves

Experiments are performed in determining the spectral composition and dynamics of radiation in a CO:N2 mixture behind the front of incident shock wave at velocities up to 6.5 km/s and initial pressures in the mixture of 1–9 torr. Absolute values of radiation intensity are obtained. It is determined that the main source of radiation under the conditions being investigated is provided by the violet system of CN. Also considered are the fourth positive system of CO and the Swan system of C2 molecule. Comparison is made of the radiation intensity and time dynamics of the molecular systems identified above.

Optical Emission Analysis of 15N: Pressure Effects and Identification of NO and Gaydon—Herman N2 Bands in the Discharge

The optical emission method, an alternative to mass spectrometry for 15N analysis, is based on measuring ratios of the intensities of the 14N2(28), 14N 15N (29), and 15N2 (30) lines of the 2→0 band of the C(3πu)→B(3πg) N2 transition near 298 nm. However, properties of the discharge are not well understood, and interferences that affect the analysis have never been explicitly identified. An efficient low-energy radio-frequency source and home-built spectrometer were used to obtain spectra over a wide range and with multiple scans. Weak extraneous bands were identified as the overlapping β andγ series of NO, not CO or OH as previously thought. Bands identified as the third positive system of CO were only observed under conditions far removed from normal practice. As tube pressure was increased from 0.3 to 1.8 kPa, the N2 intensity decreased relative to that of NO peaks. The 29/28 intensity ratio also varied with pressure, although not in a completely consistent way. A weak band underlying the 14N15N transition was identified as part of the Gaydon–Herman singlet series of N2; this interference rather than peaks from other species, may be the single factor most limiting analytical performance. Implications for the analytical method are discussed.

Double-Resonance Spectroscopy on Triplet States of CO

Double-resonance spectroscopy is used to investigate the v′ = 2 level of the b 3Σ + state and perturbing high vibrational levels ( v′ = 40-42) of the a′ 3Σ + state of CO. Single rotational levels in the a 3Π( v = 0) state are prepared via laser excitation on the Cameron band around 206 nm. Cavity-ring-down absorption spectroscopy is used to determine the absolute transition strength of this spin-forbidden transition; a value of A 0.0 = 41 ± 10 sec −1 is obtained. A laser-induced fluorescence study is performed on the metastable triplet state molecules in the region of the 2 ← 0 band of the Third Positive System of CO. From the analysis of the interacting 3Σ + states deperturbed rotational and vibrational constants as well as interaction parameters of these states are obtained. Franck-Condon factors for the transition from b 3Σ +( v′ = 2) and ( v′ = 0) to the a 3Π state are obtained from dispersion measurements.

Rotational distributions of CO from the 193 nm photodissociation of BH 3CO using nonresonant four-wave mixing for VUV generation

BH 3CO is photolyzed using an excimer laser operating at 193 nm and the nascent rotational energy distributions in CO ν″ = 0 and ν″ = 1 are measured by using laser-induced fluorescence of the fourth positive system of CO near 140 nm. The rotational energy distributions in the two manifolds can be characterized by temperatures of 362 ± 22 and 175 ± 8 K, respectively. The tunable VUV is generated using a nonresonant four-wave mixing process in Hg vapor. This technique has enabled us to extend the range of laser-induced fluorescence measurements in the vacuum ultraviolet using a single dye laser.

High-dispersion observations of alpha Bootis (K1 III) with the International Ultraviolet Explorer

Echelle spectrograms were obtained of the early-K red giant Arcturus in the far UV 1150-2000 A and middle-UV 2000-3200 A regions. Faint emission from forbidden Si II at 1892.0 A was detected. A surface flux of C IV was measured that was less than 1 percent of the solar surface flux. An observed faint spectral structure near 1380 A is believed due to the bands of the A-X fourth positive system of CO fluoresced by strong chromospheric emissions of the O I triplet. Constraints on the chromospheric structure, as evidenced by the fluorescent emissions and density-sensitive line ratios from multiplet UV lines of forbidden C II, are discussed.

Observation of the fourth positive system of CO in dissociative recombination of vibrationally excited CO +2

The CO fourth positive system obtained by dissociative recombination of CO 2 +(X̃ 2π g) ions has been observed under various conditions of CO 2 + vibrational excitation. It is shown that the CO(A 1π) vibrational distribution is directly linked to CO + 2 excitation. Implications for planetary airglows are discussed.

A search for absorption in the fourth positive system of CO in the spectrum of the planetary nebula IC 418*

A search for absorption in the fourth positive system of CO in the spectrum of the planetary nebula IC 418*

Photoelectric scanning (665-m) spectrometer for VUV cross-section measurements

A 6.65-m normal incidence vacuum spectrograph has been provided with a photoelectric scanner that is easily interchangeable with the original plate holder. The scanner consists essentially of a photoelectric detector and an exit slit that scans mechanically along the focal surface while the grating and entrance slit remain stationary. The design and construction of the 6.65-m scanning spectrometer, which operates in the 120-300-nm wavelength region, are discussed. The wavelength resolution of 0.001 nm obtained photoelectrically is better than that of any existing vacuum monochromator. The performance of the instrument is illustrated with vacuum ultraviolet scans of the (1, 5) band of the Fourth Positive system of CO in emission, and the (14, 0) band of the Schumann-Runge system of O(2) in absorption.

CO fluorescence in the extreme-ultraviolet solar spectrum

Emission lines in the fourth positive system of CO have been identified in the extreme-ultraviolet solar spectrum 1540-1660 A. These lines are excited by the C IV transition-zone lines at 1548 and 1551 A. They are strong in the spectrum of a sunspot and in parts of the adjacent active region. Some of them appear as weak, broad emission features in the quiet sun.

Scattering of solar Lyman alpha by the (14, 0) band of the fourth positive system of CO

A calculation of the fluorescent scattering spectrum of the solar Lyman alpha line by the (14, 0)band of the CO 4(+) system is presented. It is shown that emissions from the υ′ = 14 level of the A¹Π state dominate the total scattering spectrum at column densities of 1018 molecules/cm² and at ambient temperatures.

Excitation of the CO fourth positive system by the dissociative recombination of CO2+ions

The fourth positive system of CO [A ¹Π → X ¹Σ] has been excited in a static afterglow experiment by the dissociative recombination of CO2+ ions. From combined absolute optical and microwave measurements the specific recombination coefficient for exciting the CO (A → X) system was found to be (2−0.5+1) × 10−8 cm³/sec. This value represents approximately 5% of the total recombination coefficient (4.0 ± 0.5) × 10−7 cm³/sec measured in this experiment, implying that CO2+ dissociative recombination will contribute significantly to the excitation of the CO fourth positive system in the martian airglow. Corroborative electron heating experiments showed that the magnitude of the specific recombination coefficient decreased as the electron temperature was increased. Evidence was also found for the presence of vibrationally excited ions in the CO2+ plasma, a result which indicates that analogous laboratory studies on the dissociative recombination of O2+, N2+, and NO+ ions may have also involved vibrationally hot plasmas.

A curve of growth determination of the ƒ-values for the fourth positive system of CO and the Lyman-Birge-Hopfield system of N 2

The curve of growth method has been employed to determine ƒ-values for the fourth positive system of CO and the magnetic dipole and electric quadrupole components of the Lyman-Birge-Hopfield system of N 2. The transition moments are, respectively, 0.83 a 0 e, 5.9 × 10 -11 Bohr magnetons and 2.6 a 0 2 e. No significant dependence on r-centroid was found. The mean value of the ratio of the electric quadrupole to magnetic dipole ƒ-values was 0.076.

Vacuum-Ultraviolet Chemiluminescence in the Reaction of Atomic Oxygen with Acetylene

Vacuum-ultraviolet emission from the reaction of atomic oxygen with acetylene was investigated spectrographically and with photoionization detectors. The spectrum was observed at wavelengths above 1400 Å and consisted entirely of bands belonging to the fourth positive system of CO. At short wavelengths, the intensity declines rapidly, but radiation was detected with photoionization detectors filled with xylene (1425–1475 Å), NO (1100–1340 Å), and CS2 (1100–1260 Å). The high-energy limit of the emission is, correspondingly, greater than 226 kcal/mole or almost 10 eV. The dependence of the intensity on initial reactant and third-body concentrations was investigated and compared with similar concentration-dependence data for the intensity of the CH band at 4300 Å. The results show that the vacuum-ultraviolet CO emission cannot be produced by either third-body recombination of carbon and oxygen atoms or by the reaction of atomic oxygen with excited CH radicals in the A2Δ state. The reaction proposed by Becker and Bayes O+C2O→CO (A 1Π)+CO (X 1Σ)can explain the observed emission if it is assumed that a fraction of the reaction C2O radicals are vibrationally excited.

Experimental Oscillator Strengths of CO and CO+

The radiative lifetimes of the B 2Σ state of CO+ and the b 3Σ state of CO have been measured to be (1.01±0.05) 10−7 and (8.6±0.9) 10−8 sec, respectively. The oscillator strengths of the first negative system of CO+ and third positive system of CO, calculated from these lifetimes, are (7.9±0.7) 10−3 and (8.9±1.5) 10−3, respectively.

New Measurements in the Fourth Positive CO Bands

That part of the fourth positive system of CO lying between 1970A and 2800A has been remeasured together with sixteen bands not previously observed. An equation for the band heads is given, the constants of which yield the values ${D}^{\ensuremath{'}}=12.00$ volts, ${D}^{\ensuremath{'}\ensuremath{'}}=11.17$ volts for the heat of dissociation.Modifications in values of frequency have been small, while those of intensity have been rather large. Some discrepancies have been removed. Revision of intensity estimates permits a far more accurate comparison than previously with Condon's theory of intensity distribution and shows the superiority of Morse's $U(r)$ function. Using this function, the distribution of intensity among the bands of the fourth positive system agrees perfectly with Snow and Rideal's value of the moment of inertia for the normal state, $I_{0}^{}{}_{}{}^{\ensuremath{'}\ensuremath{'}}=15.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$ g ${\mathrm{cm}}^{2}$.The quantum assignment of Asundi's infra-red electronic bands has been revised.