Origin of the c /a super 3 iig/ goes to c sub 2 /x super 3 iiu/ emission in comets.
Origin of diatomic carbon Swan bands in cometary emissions due to hydrocarbon photodissociation
CARBON↗
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Spectrophotometry of comets 1967n, 1968b, and 1968c
Ikeya-Seki /1967n/, Thomas /1968b/ and Honda /1968c/ comet photoelectric spectrum, examining swan bands, continuum and reflected scattered light
Gebel, W. L.↗
Opacity probability distribution functions for electronic systems of CN and C2 molecules including their stellar isotopic forms.
The basis and techniques are presented for generating opacity probability distribution functions for the CN molecule (red and violet systems) and the C2 molecule (Swan, Phillips, Ballik-Ramsay systems), two of the more important diatomic molecules in the spectra of carbon stars, with a view to including these distribution functions in equilibrium model atmosphere calculations. Comparisons to the CO molecule are also shown. T he computation of the monochromatic absorption coefficient uses the most recent molecular data with revision of the oscillator strengths for some of the band systems. The total molecular stellar mass absorption coefficient is established through fifteen equations of molecular dissociation equilibrium to relate the distribution functions to each other on a per gram of stellar material basis.
Querci, F.↗
The dissociation of shock-heated carbon monoxide
Investigation of the dissociation kinetics of undiluted carbon monoxide over the 5,600 to 12,000 K temperature range. Data are presented that have been obtained as time-resolved pressure measurements on the end wall of a shock tube and radiation emission of a C2 Swan system (0-0 band) behind incident shock waves. The decomposition of CO is complex and includes a chain with C2 as an intermediate species. The dissociation rate for the overall process has been found to be independent of the proportions of the collision partners M = CO, C, and O. The rate constant found is on the average about 10 times that previously measured with argon as the collision partner.
Hanson, R. K.↗
Shock-tube study of carbon monoxide dissociation kinetics
Carbon monoxide dissociation-rate data were obtained over the temperature range 5600-12,000 K. The experiments were conducted with undiluted CO to emphasize rate constants applicable to molecular gas systems. Data were obtained as time-resolved pressure measurements on the end wall of a shock tube and, in some cases, as emission histories of the C2 Swan system (0-0 band) behind incident shock waves. Results confirm the presence of C2 as an intermediate species in CO decomposition.
Hanson, R. K.↗
Tail structures far from the head of Comet Kohoutek. I
Two tail structures 0.1 AU from the head of Comet Kohoutek were photographed during January 1974. One was a wavy structure resembling a helix while the other was an irregular swan-like cloud. Both features were propagating down the tail at approximately 250 km/sec, and the observed speed is probably the phase speed. We discuss the physical origin of these structures and interpret the helix as a kink instability resulting from currents flowing along the tail axis.
Hyder, C. L.↗
Measurements of the electronic transition moments of C2-band systems
Electronic transition moments of seven C2 singlet and triplet band systems, which are in the 0.2 to 1.2 micron spectral region, have been measured. The measurements were made in emission behind incident shock waves in C2H2-argon mixtures. Narrow band-pass radiometers were used to obtain absolute measurements of shock-excited C2 radiation from which absolute electronic transition moments are derived by a synthetic spectrum analysis. New results are reported for the Ballik-Ramsay, Phillips, Swan, Deslandres-d'Azambuja, Fox-Herzberg, Mulliken, and Freymark systems.
Cooper, D. M.↗
Spectrophotometry of comet Kohoutek (1973f) during pre-perihelion period
Scans of the head of comet Kohoutek obtained during the pre-perihelion period with a photoelectric spectrum scanner are discussed. The mean relative flux distributions and the continuum energy distribution of the head of comet Kohoutek are given and normalized to 479 nm. The emission features of CN, C3, Ch, and the principal Swan band sequences of C2 and Na are identified and discussed. The adopted monochromatic values relative to 479 nm are given and plotted along with the energy distribution of the sun.
Babu, G. S. D.↗
Spectrophotometry of Comet Kohoutek /1973f = 1973XII/
Spectrum scans have been obtained of Comet Kohoutek with a Fourier spectrometer at heliocentric distances from 0.55 to 1.05 AU. The useful spectral range is roughly 3800-8400 A and the resolution is about 10-15 A at 5000 A. Large variations occurred in the gas-to-dust ratio (pre- versus postperihelion) and in the relative strength of the NH2 bands (with heliocentric distance). There is a smaller change in the ratio of CN to C2 emission. The Swan bands of C2 show the customary anomaly in strengths implying highly non-Boltzmann distributions among vibrational levels. The red and violet CN system fluxes are in slightly better agreement with laboratory data on oscillator strengths than results on previous comets. Other species measured include Na, (O I), CH, and C3.
Ahearn, M. F.↗
Synthetic spectra of C2 in comets
With the key result of Krishna Swamy and O'Dell (1977), a complete fluorescence equilibrium calculation has been used to predict the detailed Swan-band spectrum in comets. A rotational Boltzmann temperature of approximately 3000 K and small changes in published molecular constants lead to a theoretical spectrum in excellent agreement with that observed. The Fox-Herzberg bands are predicted to be quite weak compared with previously observed ultraviolet features in cometary spectra. The Ballik-Ramsay bands should be observable in the near-infrared.
Ahearn, M. F.↗
Absolute measurements of the electronic transition moments of seven band systems of the C2 molecule
Electronic transition moments of seven C2 singlet and triplet band systems in the 0.2-1.2 micron spectral region were measured. The measurements were made in emission behind incident shock waves in C2H2-argon mixtures. Narrow bandpass radiometers were used to obtain absolute measurements of shock-excited C2 radiation from which absolute electronic transition moments are derived by a synthetic spectrum analysis. New results are reported for the Ballik-Ramsay, Phillips, Swan, Deslandres-d'Azambuja, Fox-Herzberg, Mulliken, and Freymark systems.
Cooper, D. M.↗
Statistical equilibrium in cometary C2. II - Swan/Phillips band ratios
Statistical equilibrium calculations have been made for both the triplet and ground state singlets for C2 in comets, using the exchange rate as a free parameter. The predictions of the results are consistent with optical observations and may be tested definitively by accurate observations of the Phillips and Swan band ratios. Comparison with the one reported observation indicates compatibility with a low exchange rate and resonance fluorescence statistical equilibrium.
Swamy, K. S. K.↗
The detection of the 5577.3 A forbidden line of O I in comets
The spectral synthesis of C2 Swan band sequence Delta V = -1 indicates the intensity of the forbidden green oxygen line of 5577.3 A to be about 3 to 5 percent of the 6300 A line. Therefore, it appears that the green line should be observable in high-resolution spectra of a bright comet. Festou and Feldman suggest red/green greater than or equal to 10 means a water parent origin.
Krishna Swamy, K. S.↗
C2 imagery of the inner coma of Comet IRAS-Araki-Alcock
May 10, 1983 observations of the comet IRAS-Araki-Alcock are analyzed to determine the spatial molecular abundance of C2 in the inner coma, via the Delta-v = +1 Swan band sequence near 4690 A. The observations indicate a deficiency of C2 emission across a projected diameter of about 2000 km that is centered on the peak of continuum emission. Comet imagery indicates a sunward-pointing coma that suggests an outburst of subsurface volatile ices through a nonvolatile surface crust, as predicted for periodic comets. These results are discussed in the framework of instrumental and observational constraints.
Oliversen, R. J.↗
Spectroscopic observations of cool degenerate star candidates
Spectroscopic observations are reported for 23 Luyten Half-Second degenerate star candidates and for 13 Luyten-Palomar common proper-motion pairs containing possible degenerate star components. Twenty-five degenerate stars are identified, 20 of which lack previous spectroscopy. Most of these stars are cool - Luyten color class g or later. One star, LP 77-57, shows broad continuum depressions similar to those in LHS 1126, which Liebert and Dahn attributed to pressure-shifted C2. A second degenerate star, LHS 290, exhibits apparent strong Swan bands which are blueshifted about 75 A. Further observations, including polarimetry and photometry, are required to appraise the spectroscopic peculiarities of these stars. Finally, five cool, sharp-lined DA white dwarfs have been observed to detect lines of metals and to determine line strengths. None of these DAs show signs of Mg b or the G band, and four show no evidence of Ca II K. The attempt to detect Ca MI in the fifth star, G199-71, was inconclusive.
Hintzen, P.↗
High precision low resolution spectrophotometry of Comets Giacobini-Zinner and Halley
Optical window (300 to 1000 nm) observations were made of Comet Halley during 12 to 14 Mar. 1986 by a scanning spectrometer. The results provide accurate spectrophotometric measurements of the principal molecular bands from the 308 nm OH through the 918 nm CN emissions. The observations can be used to tie space derived ultraviolet and groundbased infrared observations to the optical observations and to one another. Additional observations were made of comet Giacobini-Zinner on 30 September 1985 of the same OH band and the 388 nm band of CN. The Swan band sequence ratios are used to test the best models of C2, with different ratios favoring different models, calling into question the assumptions of these very complete models.
Odell, C. R.↗
The spectral development of Comet P/Halley from August 1985 to June 1986
Spectra of comet Halley were obtained every month from 1985 Aug. to 1986 June, from 5200 to 10,400 A at a spectral resolution of 12 A. Spatial extent is 200" along the slit. A variety of spatially resolved spectra with the slit along the tail and perpendicular to the tail were recorded. Emission species observed are C2, CN, NH2, H2O(+), (OI) and NaI. The 2-0 C2 Phillips band is detected at 8750 A, and from its intensity ratio of 1/9 to the 0-1 Swan band a preliminary C2 singlet to triplet intercombination probability of less than 10 to the minus 7th power is derived. Sodium emission is observed stongly only in 1986 Mar. data.
Fink, Uwe↗
Statistical equilibrium in cometary C2. IV - A 10 level model including singlet-triplet transitions
Resonance fluorescence theory was used to calculate the population distribution in the energy states of the C2 molecule in comets. Ten electronic states, each with 14 vibrational states, were used in the calculations. These new calculations differ from earlier work in terms of additional electronic levels and the role of singlet-triplet transitions between the b and X levels. Since transition moments are not known, calculations are made of observable flux ratios for an array of possible values. Comparison with existing observations indicates that the a-X transition is very important, and there is marginal indication that the b-X transition is present. Swan band sequence flux ratios at large heliocentric distance are needed, as are accurate Mulliken/Swan and Phillips/Ballik-Ramsay (1963) observations.
Krishna Swamy, K. S.↗