Spectroscopy of the C2 molecule: Valence and Rydberg states in the 7–10 eV region. An ab initio study

2001 ◽  
Vol 79 (2-3) ◽  
pp. 653-671 ◽  
Author(s):  
P J Bruna ◽  
F Grein
Keyword(s):  
Absorption Band ◽  
Ab Initio ◽  
Hubble Space Telescope ◽  
Mixed Valence ◽  
Rydberg States ◽  
Ab Initio Study ◽  
Space Telescope ◽  
First Time ◽  
Potential Curves ◽  
Singlet Transition

The potential curves of selected valence and Rydberg states of C2 lying in the 7–10 eV region are reported for the first time. The states studied, using MRCI wave funtions, include (2–5)3,1Πu, (1–3)3Σ+g, (2–5)3Σ–g, (1–3)3Δg, and relevant quintet states. The f 3Σ–g, g3Δg, and F1Πu states observed in absorption from 8.88 to 9.25 eV by Herzberg et al. have originally been assumed to be πu ® 3s Rydberg states, with respect to a 3Πu(13Πu) for the triplets and to X1Σg+ for the singlet. Our calculations partially support such assignments: f 3 Σg– corresponding to 33Σg– has mixed valence σuσgπu 3πg and Rydberg σu 2σgπu 23s character, g 3Δg corresponding to 23 Δg has a valence σuσgπu 3πg structure, while F 1 Πu(21Πu) is confirmed to be a σu 2πu 33s state. The calculated f00-values for these bands are 0.027 for f¬ a, 0.051 for g ¬ a, and 0.098 for F ¬ X. The singlet–singlet transition F ¬ X constitutes the strongest absorption band reported so far for C2. Our theoretical value agrees with f00(F¬X) = 0.10 ± 0.01 derived indirectly from interstellar data collected by the Hubble Space Telescope. The 13Σg+ (σuσgπu 3πg) state at Te = 7.57 eV lies much higher than expected by experimentalists. PACS Nos.: 31.20T, 31.50, 33.20N, 33.70. PACS Nos.: 31.20T, 31.50, 33.20N, 33.70.

The lowest-lying Rydberg states of Si2: an ab initio study

1995 ◽  
Vol 191 (1-3) ◽  
pp. 155-163 ◽  
Author(s):  
Fouad L. Sefyani ◽  
Joël Schamps
Keyword(s):  
Ab Initio ◽  
Rydberg States ◽  
Ab Initio Study

scholarly journals Eta Carinae: A Tale of Two Periastron Passages

2021 ◽  
Vol 923 (1) ◽  
pp. 102
Author(s):  
Theodore R. Gull ◽  
Felipe Navarete ◽  
Michael F. Corcoran ◽  
Augusto Damineli ◽  
David Espinoza ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Hubble Space Telescope ◽  
Wavelength Dependence ◽  
Primary Star ◽  
Space Telescope ◽  
Eta Carinae ◽  
Secondary Star ◽  
Order Of Magnitude ◽  
Far Ultraviolet ◽  
First Time

Abstract Since 2002, the far-ultraviolet (FUV) flux (1150–1680 Å) of Eta Carinae, monitored by the Hubble Space Telescope/Space Telescope Imaging Spectrograph, has increased by an order of magnitude. This increase is attributed to partial dissipation of a line-of-sight (LOS) occulter that blocks the central core of the system. Across the 2020 February periastron passage, changes in the FUV emission show a stronger wavelength dependence than occurred across the 2003 July periastron passage. Across both periastron passages, most of the FUV spectrum dropped in flux then recovered a few months later. The 2020 periastron passage included enhancements of FUV flux in narrow spectral intervals near periastron followed by a transient absorption and recovery to pre-periastron flux levels. The drop in flux is due to increased absorption by singly ionized species as the secondary star plunges deep into the wind of the primary star, which blocks the companion’s ionizing radiation. The enhanced FUV emission is caused by the companion’s wind-blown cavity briefly opening a window to deeper layers of the primary star. This is the first time transient brightening has been seen in the FUV comparable to transients previously seen at longer wavelengths. Changes in resonance line-velocity profiles hint that the dissipating occulter is associated with material in LOS moving at −100 to −300 km s−1, similar in velocity of structures previously associated with the 1890s lesser eruption.

scholarly journals Quantifying the AGN-driven outflows in ULIRGs (QUADROS) IV: HST/STIS spectroscopy of the sub-kpc warm outflow in F14394+5332

2019 ◽  
Vol 488 (2) ◽  
pp. 1813-1821 ◽  
Author(s):  
C Tadhunter ◽  
L Holden ◽  
C Ramos Almeida ◽  
D Batcheldor
Keyword(s):  
Hubble Space Telescope ◽  
Outer Part ◽  
Ionization State ◽  
Space Telescope ◽  
High Ionization ◽  
Mass Outflow ◽  
Outflow Region ◽  
First Time ◽  
Imaging Spectrograph ◽  
Luminous Infrared Galaxy

ABSTRACT Considerable uncertainties remain about the nature of warm, AGN-driven outflows and their impact on the evolution of galaxies. This is because the outflows are often unresolved in ground-based observations. As part of a project to study the AGN outflows in some of the most rapidly evolving galaxies in the local Universe, here we present Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) observations of F14394+5332E that resolve the sub-kpc warm outflow for the first time in an ultra-luminous infrared galaxy. The observations reveal a compact, high-ionization outflow region (rmax ∼ 0.9 kpc) set in a more extensive (rmax ∼ 1.4 kpc) halo that is kinematically quiescent and has a lower ionization state. A large line width (600 < FWHM < 1500 km s−1) is measured throughout the outflow region, and the outflowing gas shows a steep velocity gradient with radius, with the magnitude of the blueshifted velocities increasing from ∼500 to 1800 km s−1 from the inner to the outer part of the outflow. We interpret the observations in terms of the local acceleration, and hydrodynamic destruction, of dense clouds as they are swept up in a hot, low-density wind driven by the AGN. We discuss the implications for measuring the mass outflow rates and kinetic powers for the AGN-driven outflows in such objects.

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