Comet-tail System Research Articles

First observation of the Comet-Tail [formula omitted] system in the [formula omitted] cation

In the emission spectrum of the 12C17O+ isotopologue the Comet-Tail (A2Πi→X2Σ+) system has been observed and analysed for the first time. 1215 spectral transitions in the 16 950 to 22 000 cm−1 region, belonging to three A−X (1−0,1−1 and 1−2) bands, were recorded with the Fourier-transform spectrometer and measured with an accuracy of 0.01 cm−1. As a result of analysis, 15 molecular parameters of the A2Πi(v=1) and X2Σ+(v=0,1,2) levels were obtained. The ro-vibronic term values of the A2Πi(v=1) level were also determined. Moreover, a very weak A2Πi(v=1)∼X2Σ+(v=11) perturbation of a complex, spin-orbit, spin-electronic and L−uncoupling character was identified and worked out. A percentage 2Π character of the A2Πi(v=1) and X2Σ+(v=11) levels was considered in detail.

ELECTRONIC EXCITATION AND CHARGE TRANSFER PROCESSES IN COLLISIONS OF H+, H$_2^+$, AND H$_3^+$ IONS WITH CARBON MONOXIDE AT TYPICAL SOLAR-WIND VELOCITIES

Luminescence in the 200-580 nm spectral region was observed in the collisions of H+, H, and H with CO in the 50-1000 eV projectile energy range. Using computer simulations, we have identified emission of the following products in the observed spectra: the CO+(A-X) comet-tail system, CO+(B-X) first negative system, CO+(B-A) Baldet-Johnson system, and CO(b-a) third positive system. Also, an emission from atomic hydrogen (Hβ line at 486nm) has been observed. From the analysis of the experimental spectra, we have determined the absolute emission cross-sections for the formation of the observed products. Computer simulations gave the excited-product population distributions over vibrational and rotational energy levels. The vibrational level distribution from the CO+(A-X) comet-tail system is compared with the data for CO excited by 100 eV electrons and extreme ultraviolet radiation (XUV) photons. We have used these data to analyze the excitation conditions in the comet Humason (1961e). From the vibrational population distributions observed in the comet, we found that this distribution can be reproduced if electrons produce 25%, protons 70%, and XUV photons produce 5% of the emitting molecules. We find that the ratio of the CO+(B-X) emission to the sum of two main emissions (CO+(A-X)+CO+(B-X)) is velocity dependent and does not depend on the projectile ion type. For small velocities (below 100 km s–1) the ratio is about 5%, while for higher velocities it increases to 30%. For these data, we have found an empirical formula that satisfactorily describes the experimental data: R = R max(1 – v th/v), (where R max = 33%, v th = 87 km s–1). This could be used to infer the velocity of ions producing the observed emission of CO+ products.

Global analysis of the Comet-tail system of 12C16O+

A global analysis of the ro-vibrational spectra of 19 bands in the comet-tail (A2Πi−X2Σ+) system of the 12C16O+ cation is presented, and the precise molecular constants of the vibrational levels involved are obtained via a weighted nonlinear least-squares fitting procedure. Furthermore, the resultant precise equilibrium molecular constants enable us to achieve accurate Rydberg—Klein—Rees (RKR) potential curves for both the A and X states, yielding the accurate Franck—Condon factor and band origin of each band in this system.

Rotational analysis of weak (4, 6) hot band in the comet-tail ( A2Π i– X2Σ +) system of the CO +

The ro-vibrational spectrum of the weak (4, 6) hot band in the comet-tail ( A 2Π i – X 2Σ +) system of CO + is observed by employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. One hundred and twenty-four spectral lines are assigned to this band; thus, precise molecular constants of the levels involved are obtained from a weighted nonlinear least-squares fitting procedure combining with our previous spectrum of the (3, 6) band.

Rotational analysis of the (3, 6) band in the comet-tail ( A2Π i – X2Σ +) system of CO +

The direct observation and rotational analysis of the (3, 6) band in the comet-tail ( A 2Π i – X 2Σ +) system of CO + are carried out for the first time employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. That 193 lines are assigned to this band ranging from 12 100 to 12 370 cm −1 results in most accurate molecular constants by nonlinear least-squares fitting procedure employing the effective Hamiltonians.

Study of (1, 4) band in the comet–tail ( A2Π i– X2Σ +) system of CO +

Ro-vibrational spectrum of the (1, 4) band in the comet–tail system of CO + cation is observed employing the optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy in the range of 13 189–13 472 cm −1. Two hundred and eighteen spectral lines are assigned to 12 branches of this band for the first time, thus, precise molecular constants of the levels involved are obtained by nonlinear least-squares fitting procedure combining with our previous spectrum of the (1, 2) band.

New analysis of the Comet-Tail ( A2Π i − X2Σ +) system in the 14C 16O + isotopic molecule

The emission spectra of the 0–2, 4–2, and 6–1 bands of the Comet-Tail ( A 2Π i − X 2Σ +) system in the 14C 16O + isotopic molecule, comprising nearly 600 lines, have been recorded and analyzed for the first time. The spectra have been photographed under high resolution by using conventional spectroscopy, and it was possible to separate and observe most of the lines of all the 12 branches of this transition. The reduction of the individual bands’ spectra has been performed by nonlinear least-squares procedure and by means of effective Hamiltonians of Brown et al. the rovibronic structure parameters have been obtained. The currently investigated bands of the Comet-Tail system and the earlier analyzed bands of the A − X and B − A systems in the 14C 16O + molecule have been merged together. The results of this global fit made it possible to derive a new set of the equilibrium molecular constants for the A and X states. Then the RKR potential curve parameters for both A and X states and Franck-Condon factors as well as r-centroids for the A − X transition have been calculated for the 14C 16O + molecule.

New spectroscopic studies of the Comet–Tail (A 2Π i–X 2Σ +) system of the CO + molecule

In the electronic emission spectrum of the 12C 16O + molecule, 11 bands of the Comet–Tail ( A 2Π i – X 2Σ +) system have been recorded and analyzed. Spin splitting in most of the observed lines of the 0–2, 1–0, 2–0, 2–1, 3–0, 4–0, 4–2, 6–0, 7–0, 7–1, and 8–1 bands, comprising nearly 3400 lines, has been recorded under high resolution by conventional spectroscopy. The rotational analysis of bands has been performed by nonlinear least-squares procedures and by means of effective Hamiltonians of Brown et al. and the rovibronic structure parameters have been obtained. The data of bands of the A– X system and earlier analyzed bands of the B– X and B– A systems have been merged together. As a result of this global fit, the state of information about the energy structure has been significantly enlarged for the A state and enlarged and improved for the X state. Also RKR potential curves for both states and Franck–Condon factors as well as r-centroids of the Comet–Tail system of CO + have been calculated.

Analysis of the Comet-Tail (A2Πi–X2Σ+) Bands of 13C16O+

In the electronic emission spectrum of the isotopic carbon monoxide ion 13C16O+ molecule, seven bands of the comet-tail (A2Πi–X2Σ+) system have been recorded and analyzed. The spin splitting in most observed lines of the bands 1–0, 2–0, 3–0, 4–0, 5–0, 2–1, and 7–1 comprising over 1900 lines has been recorded under high resolution by using conventional spectroscopy. The rotational analysis of bands has been performed by nonlinear least-squares procedures and by means of effective Hamiltonians of Brown et al., the rovibronic structure parameters have been obtained. As a result of multistaged and merged analysis of the currently obtained bands of the A–X system and of the bands of the B–X system obtained earlier the state of information about the energy structure has been significantly enlarged for the A state and enlarged and improved for the X state. Also RKR potential curves have been calculated for both states and Franck–Condon factors as well as r-centroids of the comet-tail system of 13C16O+.

Study on the (1, 2) and (2, 3) bands in the comet-tail system of 12C16O+ by optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy

Optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy was employed to observe the absorption spectra of the (1, 2) and (2, 3) bands of the comet-tail (A2 Πi—X2Σ+) system of CO+ in the visible region. A rotational analysis was performed to obtain more precise molecular constants for the four involved vibrational levels. Moreover, accurate RKR potentials and the Franck-Condon factors are given for these four vibronic levels. This calclulation reveals that v = 0, 5, 10 vibrational levels in the A state will be perturbed by the v = 10, 14, 18 levels in the × state, respectively, and the v = 9 level might be weakly perturbed by the v = 17 level.

The Comet-Tail (A2Πi–X2Σ+) System of 12C16O+: A Reinvestigation

The emission spectrum of the comet-tail (A2Πi–X2Σ+) system of 12C16O+ produced in the cathode glow of a hollow-cathode discharge tube and photographed in the spectral region 3345–8500 Å at high resolution was reinvestigated. Detailed rotational analysis of 10 bands involving 5 vibrational levels v = 0 to 4 of each of the A and X states was carried out. Spin-splitting of the rotational levels was observed for the analyzed bands. The observed intensity distribution of the branches is found to be in good agreement with theoretical calculations. Molecular constants for both the A and X states were obtained from a global fit of the present data of the A–X system and the infrared and microwave data available from the literature for v = 0, 1, 2, 3, and 4 of state X, using effective Hamiltonian for the A2Π state and matrix elements for both A and X states. The present work suggests that the A2Πi state changes from Hund's case (a) at low J values to Hund's case (b) at high J values.

Excitation of CO+ and NO+ Electronic States Via Single-electron Capture by B2+ Ions

High-resolution translational energy loss spectrometry was performed to obtain the spectra for single-electron capture by 6 keV B2+ ions in collision with CO and NO molecules, to complement a previous investigation involving O2 and N2 targets. The spectrum for CO consists of eight well defined peaks, three of which correspond to capture into the ground state of CO+[X2Σ+] dominated by the 0–0 molecular transition. One intense peak and a subsidiary one are identified as capture into the first excited electronic state of CO+, responsible for subsequent emission of the comet-tail system CO+[A 2Πi→X 2Σ+]. The B 2Σ+ state of CO+, the upper electronic state of the Baldet-Johnson [B 2Σ+→A 2Σi] and the first negative [B 2Σ+→X 2Σ+] bands, is also accessed through two capture channels. The NO spectrum exhibits one intense narrow peak dominated by capture into the second triplet state of NO+ [b 3Π], together with subsidiary features which may involve capture into the ground X 1Σ+ and excited singlet (A 1Π,A′ 1Σ+, W 1Δ) and triplet (b 3Π, a 3Σ+, b′ 3Σ−) manifolds. The NO spectrum is complicated by energy overlap of relevant capture channels, which makes unambiguous identification difficult. © 1997 John Wiley & Sons, Ltd.

Collisional excitation of the Comet-Tail system of CO + [ A2Π i- X2Σ +

High-resolution translational energy spectroscopy (0.1 eV full width at half maximum) has been performed on 3-keV CO + ions scattered off Ar, N 2, O 2, CO, and NO. Excitation of the Comet-Tail system [ A 2Π i ← X 2Σ +] of CO + is prominent in all the spectra. Characteristic singlet-triplet electronic transitions of the target molecules are also present with N 2, O 2, and CO as target gases.

The comet-tail (A-X) system of CO(+) - Precise molecular constants of its 2Sigma(+), A 2 Pii, and B 2Sigma(+) states

view Abstract Citations (28) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Comet-Tail (A--X) System of CO +: Precise Molecular Constants of Its X 2 Sigma +, A 2 Pi i, and B 2 Sigma + States Haridass, C. ; Prasad, C. V. V. ; Reddy, S. P. Abstract The comet-tail (A 2 Pii-X 2Sigma(+)) system of the molecular ion (C-12)(O-16)(+), excited in the cathode glow of a hollow-cathode discharge tube of special design, was photographed in the spectral region 3400-8500 A. Of the 17 observed bands with v-prime = 0-8 and v-double prime = 0-4, the rotational structure of 12 bands with v-prime = 0-4 and 6 and v-double prime = 0-4 was analyzed. An effective Hamiltonian was used to obtain the molecular constants of the individual bands from their wavenumber data and the constants for the A and X states were then determined by merging the molecular constants thus obtained by the method of correlated least-squares fit. Recent experimental data of (C-12)(O-16)(+) available for the first negative (B 2Sigma(+)-X 2Sigma(+)) and the Baldet-Johnson (B 2Sigma(+)-A 2Pii) systems and for the IR spectrum involving v = 0 and 1, and the microwave spectra involving v = 0, 1, and 2, of its ground state X, were reanalyzed using this effective Hamiltonian. A precise set of molecular constants for the X, A, and B states of (C-12)(O-16)(+) is determined by the procedures referred to above. The astrophysical importance of the spectra of CO(+) is also briefly outlined. Publication: The Astrophysical Journal Pub Date: April 1992 DOI: 10.1086/171183 Bibcode: 1992ApJ...388..669H Keywords: Carbon Monoxide; Comet Tails; Electron States; Molecular Ions; Positive Ions; Cathode Glow; Ground State; Hollow Cathodes; Infrared Spectra; Microwave Spectra; Astrophysics; LINE: IDENTIFICATION; MOLECULAR DATA; TECHNIQUES: SPECTROSCOPIC full text sources ADS |

The first negative ( B2Σ +- X2Σ +) system of 13C 18O +

The first negative ( B 2Σ +- X 2Σ +) system of the molecular ion 13C 18O + excited in the cathode glow of a hollow-cathode discharge tube was recorded in the spectral region 2110–2755 Å. Of the 22 bands observed with v′ = 0 to 4, and v″ = 0 to 7, the rotational structure of 13 bands was analyzed. The spin splitting of the spectral lines, which is a characteristic of a 2Σ +- 2Σ + transition, was observed in several bands. The molecular constants obtained from the analysis of the individual bands of this system were first merged together by the method of correlated least-squares fit. The resulting constants were then merged with those obtained from our recent studies of the comettail ( A 2Π i - X 2Σ +) system [C. V. V. Prasad and S. P. Reddy, J. Chem. Phys., 90, 3010 (1989)] and the Baldet-Johnson ( B 2Σ +- A 2Π i) system [S. P. Reddy and C. V. V. Prasad, J. Chem. Phys., 91, 1972 (1989)] of 13C 18O +, and a precise set of molecular constants for the X, A, and B states was obtained. Some of the derived constants of 13C 18O + in cm −1 are X 2 Σ + A 2 Π i B 2 Σ + B e 1.79468(2) 1.44258(2) 1.63374(2) α e 0.016440(3) 0.016791(4) 0.026003(7) ω e 2110.039(4) 1488.940(4) 1650.665(4) ω ex e 13.738(2) 12.411(2) 23.983(1) ω ey e −0.0032(2) 0.0228(2) - The astrophysical importance of this work is also briefly discussed.

The Baldet–Johnson (B 2Σ+–A 2Πi) system of 13C18O+

The rotational structure of the 1–0, 0–0, and 0–1 bands of the Baldet–Johnson (B 2Σ+–A 2Πi) system of the molecular ion 13C18O+, excited in the cathode glow of a hollow-cathode discharge tube, was recorded in the spectral region 3700–4225 Å and analyzed. An effective Hamiltonian proposed by Brown et al. [J. M. Brown, E. A. Colbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294 (1979)] was used to obtain the molecular constants from the wave number data of these three bands. These molecular constants were first ‘‘merged’’ together and the resulting constants were then ‘‘merged’’ with those of the comet-tail (A 2Πi–X 2Σ+) system of 13C18O+ recently reported by us [C. V. V. Prasad and S. P. Reddy, J. Chem. Phys. 90, 3010 (1989)] to obtain a unique set of constants for the X 2Σ+, A 2Πi, and B 2Σ+ states. Some of the derived constants of 13C18O+ (in cm−1) are for X 2Σ+: Be=1.794 28(4), αe=0.016 61(3), ωe =2110.27(2), and ωexe =13.81(6); for A 2Πi : Be=1.441 92(4), αe=0.016 76(1), ωe =1488.99(2), ωexe =12.454(7), and ωeye =0.0279(8); for B 2Σ+: Be=1.632 62(4), αe=0.025 49(2), ωe=1657.56, and ωexe =27.42.

The comet-tail (A 2Πi–X 2Σ+) system of 13C18O+

The comet-tail (A2Πi–X2Σ+) system of the molecular ion 13C18O+, excited in the cathode glow of a hollow-cathode discharge tube, was recorded in the spectral region 3620–6165 Å. Of the nine bands observed with v′=0 to 5 and v″=0 to 2, the rotational structure of 8 bands was analyzed. Brown’s effective Hamiltonian [J. M. Brown, E. A. Colbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294 (1979)] was used to obtain the molecular constants of the individual bands from their wave number data. By ‘‘merging’’ the molecular constants thus obtained, a unique set of constants for the X2Σ+ and A2Πi states was obtained. Some of the derived molecular constants of 13C18O+ in units of cm−1 (except re in Å) are: X2Σ+: Be=1.794 28(5), re=1.1156, αe=0.016 66(3), ΔG(1/2)=2082.69; A2Πi: Be=1.441 73(5), re=1.2445, αe=0.016 71(1), ωe=1488.07, ωexe=12.16.

Comet-tail ( A- X) band system of isotopic CO + molecule

The bands of the A 2Π i - X 2Σ + comet-tail system (370–620 nm) of 12C 16O + and 12C 18O + molecule have been recorded in emission from a hollow cathode discharge lamp using a high-resolution spectrograph. The vibrational numbering of the previous authors was confirmed by measuring the isotope displacement. The rotational analysis of the (0-2), (2-0), (3-0), and (4-0) bands has been carried out for the first time. Molecular constants b e, D e, H e, A 0, A 1, γ 0, P 0, and q 0 for A 2Π and B e, D e, H e, and γ 0 for X 2Σ + have been derived.

CO(+) fluorescence in comets

Calculations of the fluorescent equilibrium of the CO(+) molecule to determine the Swings and Greenstein effects as a function of heliocentric radial velocity have been carried out. The previously ignored Baldet-Johnson (B-A) bands were included in addition to the comet tail (A-X) and first negative (B-X) bands, thus allowing a determination of the absolute intensities of all bands. As with certain other molecules such as OH and CN, the Swings effect on individual lines is large enough that integrated band fluxes in the comet tail system also exhibit the Swings effect. The flux variations for velocities in the range - 50 to + 350 km/s have been calculated and may be used to map the acceleration of CO(+) ions into the tail, even with low dispersion spectra.

CO/+ Fluorescence in Comets

Calculations of the fluorescent equilibrium of the CO(+) molecule to determine the Swings and Greenstein effects as a function of heliocentric radial velocity have been carried out. The previously ignored Baldet-Johnson (B-A) bands were included in addition to the comet tail (A-X) and first negative (B-X) bands, thus allowing a determination of the absolute intensities of all bands. As with certain other molecules such as OH and CN, the Swings effect on individual lines is large enough that integrated band fluxes in the comet tail system also exhibit the Swings effect. The flux variations for velocities in the range - 50 to + 350 km/s have been calculated and may be used to map the acceleration of CO(+) ions into the tail, even with low dispersion spectra.