Predissociation effects in the A, B, and C states of CH and the interstellar formation rate of CH via inverse predissociation

Brzozowski, J.; Bunker, P. R.; Elander, Nils; Erman, P.

doi:10.1086/154509

Cited by 180 publications

(90 citation statements)

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“…We calculated line positions of other satellite branches after we calculated B state energy levels using the line positions of the main branch lines and X state energy levels. For an oscillator strength value, we used 3.1 ± 0.2 x 10-3, which was derived from an average of four lifetime measurements (Brooks and Smith, 1974;Anderson et al, 1975;Brzozowski et al, 1976;Ortiz and Campos, 1982). The ratio of adopted oscillator strengths for the B-X (0-0) and A-X (0-0) bands is 0.61, which is in excellent agreement with experimental values (Linevsky, 1967;Garland and Crosley, 1985) and a theoretical estimate (Hinze et al, 1975).…”

Section: Modelingsupporting

confidence: 66%

“…We used formulae presented in Table 1 of Schadee (1975) for the calculations of the Holn-London factors for the first rotational lines. After a thorough search through the literature, we conclude that the best oscillator strength is 5.1 ± 0.15 x 10-3, which was derived from an average of the best four lifetime measurements (Brzozowski et al, 1976;Becker et al, 1980;Ortiz and Campos, 1982;Bauer et al, 1989). This value is in excellent agreement with a refined and extensive theoretical treatment by Larsson and Siegbahn (1983).…”

Section: Modelingmentioning

confidence: 95%

“…Einstein A and B coefficients were calculated using the same ways as described in the previous paragraph for the A-X system. Significant predissociations occur in the A state as well as in the B and C states of CH (Brzozowski et al, 1976). We consider only stable energy levels in the A and B states in the fluorescence calculations.…”

Section: Modelingmentioning

confidence: 99%

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High-Resolution Spectroscopy of the A-X and B-X System of CH in Comet Austin (1990 V).

Kim

Brown²,

Spinrad³

1997

J. geomagn. geoelec

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We analyzed the A-X(0-0) band of CH, which appears in high-resolution spectra of comet Austin (1990 V), in order to understand fluorescence and collisional processes that influence the rotational structure of the A-X(0-0) band. Some of the weak lines of the A-X (0-0) band are clearly resolved, which have not been previously resolved with relatively low-resolution spectroscopy. We unambiguously confirmed the B-X (0-0) band lines around 3890 A, which had been suspected previously, but it had not been clearly identified because of strong adjacent CN and C3 bands. In order to analyze the cometary spectra we have conducted two different fluorescence calculations: a single-cycle fluorescence and fluorescent equilibrium. The fluorescent equilibrium model includes infrared and ultraviolet fluorescence processes as well as electron and neutral collisional effects, and therefore the model is a function of cometocentic distance. We found that single-cycle fluorescence models with a Boltzmann distribution in the X state fit the observed spectra better than the fluorescent equilibrium models. However, single-cycle fluorescence models with two different temperatures (130 K for F1 state and 250 K for F2 state) in the X state fit the Austin spectra significantly better than the single-cycle fluorescence model with the same temperature (150 K) for F1 and F2 states. This suggests that we are observing two different Boltzmann distributions of nascent, shortlife CH radicals right after they were produced by photodissociations of parent molecules. We presented g-factors of the A-X (0-0) and B-X (0-0) bands as a function of heliocentric velocity based on single-cycle fluorescence models with a 150 K distribution in the X state. We have calculated the expected intensity of the fundamental band (v" = 1 --+ 0) of CH and discussed the detectability of this band near 2730 cm-1. We also discussed possible parent molecules of CH and long lifetimes of the parent molecules, which may explain extensive emissions of CH up to 105 km from the nucleus despite its short lifetime.

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Section: Modelingsupporting

confidence: 66%

Section: Modelingmentioning

confidence: 95%

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High-Resolution Spectroscopy of the A-X and B-X System of CH in Comet Austin (1990 V).

Kim

Brown²,

Spinrad³

1997

J. geomagn. geoelec

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“…Therefore, we have calculated the synthetic CH spectrum utilizing the LIFBASE molecular spectra simulation program [31] with the use of vibrational and rotational constants of the A 2 Δ, B 2 Σ + and X 2 Π r electronic states of CH from [32][33][34][35][36][37]. Similar computer procedure, employed in the analysis of spectra of diatomic molecules, occurring in cation-and photoninduced fragmentation of five-and six-membered heterocycles, has been recently proven to be efficient and dependable [15,18,27,28,38].…”

Section: Hementioning

confidence: 99%

Interactions of protons with furan molecules studied by collision-induced emission spectroscopy at the incident energy range of 50–1000 eV

Wąsowicz

Pranszke

2016

Eur. Phys. J. D

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Abstract.Investigations of the ion-molecule reactions provide insight into many fields ranging from the stellar wind interaction with interstellar media, up to medicine and industrial applications. Besides the applications, the understanding of these processes is itself a problem of fundamental importance. Thus, interactions of protons with the gas-phase furan molecules have been investigated for the first time in the energy range of 50-1000 eV exploiting collision-induced emission spectroscopy. Recorded spectra reveal emission of the atomic H β to H θ lines of the hydrogen Balmer series and the molecular bands of vibrationally and rotationally excited diatomic CH fragments created in the A 2 Δ and B 2 Σ − electronic states. The measurements of the emission yields of the excited fragments by recording their intensities at different projectile energies have been performed. The highest yields have been observed for production of hydrogen atoms which intensities rapidly decreased with increasing principal quantum number n. From the H (n = 4-7) intensity ratios depopulation factors of hydrogen excited states have been determined at each impact energy and possible collisional mechanisms leading to enhanced production of the hydrogen atoms have been suggested. We compare and discuss our results with improved data set of proton collisions with tetrahydrofuran (THF) molecules, the hydrogenated derivatives of furan.

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“…This region includes the band head of the (0-0), (1-1), (2-2) bands of the A 2 D-X 2 P transitions of CH. The dissociation potential used was 3.465 eV from Brzozowski et al (1976), and the log gf values of the electronic transitions were modified to reproduce the solar spectrum by using the solar abundance of carbon from Anders & Grevesse (1989) and the Kurucz solar spectrum. We found a corrective factor of À0.3 dex in log gf and a shift of À0.05 Å in wavelength.…”

Section: Abundancementioning

confidence: 99%

Stellar Archaeology: A Keck Pilot Program on Extremely Metal-Poor Stars From the Hamburg/ESO Survey. III. The Lead (P[CLC]b[/CLC]) Star HE 0024−2523

Lucatello

Gratton

Cohen

et al. 2003

The Astronomical Journal

128

147

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We present a detailed abundance analysis, including spectral syntheses, of a very metal-poor ([Fe/H] ' À2.7) peculiar main-sequence star (HE 0024À2523) detected during the course of the Keck Pilot Program. Radial velocities of this star were obtained during four different observing runs over a time span of 1.1 yr and demonstrate that it is clearly a short-period spectroscopic binary. An orbital solution was obtained, and orbital parameters were determined with high precision. The rotational velocity was also measured (v rot sin i = 9.7 AE 1.5 km s À1 ); rotation appears likely to be synchronous with the orbit. The abundance analysis and spectral syntheses indicate that the object is a CH star characterized by extreme s-process enrichment, likely due to mass accretion from an evolved companion that has now probably become a white dwarf. The lead (Pb) abundance of (HE 0024À2523) is very high, the same as that of the recently discovered lead-rich, metal-poor star CS 29526-110, [Pb/Fe] = +3.3. The abundance ratio of the heavy to light s-elements, as characterized by Pb and Ba, [Pb/Ba] = +1.9, is the highest yet found for any metal-poor star and is about 0.7 dex higher than that of CS 29526-110. On the basis of the measured isotopic ratio of carbon (C 12 /C 13 $ 6) we argue that the mass donor must have had an original mass of at least $3 M . The unusually short period of this CH star suggests that it underwent a past common-envelope phase with its evolved companion. Our results are compared with the latest available models for asymptotic giant branch yields and s-process nucleosynthesis. We also discuss the possible connection between HE 0024À2523, the lithium depletion of halo stars, and halo blue straggler formation.

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Predissociation effects in the A, B, and C states of CH and the interstellar formation rate of CH via inverse predissociation

Cited by 180 publications

References 0 publications

High-Resolution Spectroscopy of the A-X and B-X System of CH in Comet Austin (1990 V).

High-Resolution Spectroscopy of the A-X and B-X System of CH in Comet Austin (1990 V).

Interactions of protons with furan molecules studied by collision-induced emission spectroscopy at the incident energy range of 50–1000 eV

Stellar Archaeology: A Keck Pilot Program on Extremely Metal-Poor Stars From the Hamburg/ESO Survey. III. The Lead (P[CLC]b[/CLC]) Star HE 0024−2523

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