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Abstract
Rate coefficients for inelastic processes in low-energy Co + H, 
 
 
 
 
 
 Co
 
 +
 
 +
 
 
 H
 
 −
 
 
 
 
 , 
 
 
 
 
 
 Co
 
 +
 
 +
 H
 
 
 
 , and 
 
 
 
 
 
 Co
 
 
 2
 +
 
 
 +
 
 
 H
 
 −
 
 
 
 
 collisions are estimated using the quantum simplified model. Considerations include 44 triplet and 55 quintet molecular states of CoH, as well as 91 molecular states of CoH
 
 
 
 
 +
 
 
 
 . The estimations provide the rate coefficients for the 4862 partial processes (mutual neutralization, ion-pair formation, excitation, and de-excitation) in the neutral CoH system, and for the 
 
 
 
 8190
 
 
 
 partial processes in the ionized CoH
 
 
 
 
 +
 
 
 
 system, 
 
 
 
 13
 ,
 052
 
 
 
 processes in total. At 
 
 
 
 T
 =
 6000
 
 
 
 K, the rate coefficients with the largest values around 
 
 
 
 6
 ×
 
 10
 
 −
 8
 
 
 
 
 
 cm
 
 3
 
 
 
 s
 
 
 −
 1
 
 
 
 
 
 correspond to the mutual neutralization processes into the 
 
 
 
 Co
 (
 
 e
 2
 
 F
 )
 +
 H
 
 
 
 and 
 
 
 
 
 Co
 +
 
 
 (
 
 g
 5
 
 F
 )
 
 +
 H
 
 
 
 final channels in the neutral and ionized systems, respectively. Among the excitation and de-excitation processes in Co + H and in Co
 
 
 
 
 +
 
 
 
 + H collisions, at 
 
 
 
 T
 =
 6000
 
 
 
 K, the largest rate coefficients have values around 
 
 
 
 7
 ×
 
 10
 
 −
 9
 
 
 
 
 
 cm
 
 3
 
 
 
 s
 
 
 −
 1
 
 
 
 
 
 and correspond to the processes 
 
 
 
 
 Co
 (
 
 y
 2
 
 
 S
 ∘
 
 )
 +
 H
 
 →
 
 Co
 (
 
 e
 2
 
 F
 ;
 
 
 v
 4
 
 
 D
 ∘
 
 )
 +
 H
 
 
 
 
 and 
 
 
 
 
 
 Co
 +
 
 
 (
 
 h
 3
 
 P
 )
 
 +
 H
 
 →
 
 
 Co
 +
 
 
 (
 
 g
 3
 
 P
 ;
 
 
 g
 5
 
 P
 ;
 
 
 g
 5
 
 F
 )
 
 +
 H
 
 
 
 
 , respectively. The calculations single out inelastic processes important for non-local thermodynamic equilibrium (NLTE) modelling of Co I and Co II spectra in stellar atmospheres. The test NLTE calculations are carried out, and it is found that the new collision rates have a strong effect on the line formation and NLTE abundance corrections.
Highlights
Determination of the stellar absolute and relative abundances for different chemical elements is one of the fundamental problems in modern astrophysics, see, e.g., reviews [1,2] and references therein, for example, for understanding the Big Bang, stellar evolution, and microscopic processes in stars
Local Thermodynamic Equilibrium (LTE) modelings of stellar spectra provide not sufficiently accurate results, and non-Local Thermodynamic Equilibrium (NLTE) modelings are used for more accurate treatments [1,2]
Calculations of the rate coefficients for inelastic processes in low-energy Co + H, Co+ + H−, Co + H, and Co2+ + H− collisions are performed by means of the quantum simplified model [28,29]
Summary
Determination of the stellar absolute and relative abundances for different chemical elements is one of the fundamental problems in modern astrophysics, see, e.g., reviews [1,2] and references therein, for example, for understanding the Big Bang, stellar evolution, and microscopic processes in stars. The lack of reliable data on H-collisional data, i.e., inelastic processes in collisions of atoms and positive ions of a treated chemical element with hydrogen atoms and negative ions, brings the main uncertainty in NLTE modelings due to the highest abundance of hydrogen in the Universe. The astrophysical origin of Co is still poorly understood, as the models of Galactic chemical evolution fail to explain the abundances of Co relative to Fe in the disk and in the halo (e.g., Andrews et al [23], Côté et al [24]) This mismatch is commonly attributed to the uncertainties of core-collapse and SN I models [20]. We compare our results with our previous predictions and quantify the importance of quantum H-collision data in the NLTE modelling of Co lines
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