Recently, in 2020, Stark broadening parameters have been measured for spectral lines belonging to 75 vanadium II (V II) multiplets. For some of them, there are published calculations in the literature. However, these lines are not sufficient for the analysis of the lines present in the metal-poor star HD 8493. When new calculations by the Griem approximation are performed and compared with the experimental results, in some cases there is a difference of a factor of 7. It is clear that the problem lies, as already suggested some years ago in a theoretical paper by Douglas H. Sampson, in the poor approximation proposed by van Regemorter for the Gaunt factors used in the Griem approximation. In this work, we have performed broadening measurements of 3276.12 and 3715.46 Å V II lines that confirmed the previous measurements of 2020. Subsequently, we performed a more accurate calculation using the procedure to calculate the Gaunt factors suggested by Sampson, obtaining results very close to the experimental values. These allowed us to assume that the calculations performed for 56 lines ranging between 3700 and 4600 Å (present in the photospheres of the Sun and the metal-poor star HD 8493), and without experimental information, are more accurate using the Gaunt factors proposed by Sampson.
Recently, in 2020, Stark broadening parameters have been measured for spectral lines belonging to 75 vanadium II (V II) multiplets. For some of them, there are published calculations in the literature. However, these lines are not sufficient for the analysis of the lines present in the metal-poor star HD 8493. When new calculations by the Griem approximation are performed and compared with the experimental results, in some cases there is a difference of a factor of 7. It is clear that the problem lies, as already suggested some years ago in a theoretical paper by Douglas H. Sampson, in the poor approximation proposed by van Regemorter for the Gaunt factors used in the Griem approximation. In this work, we have performed broadening measurements of 3276.12 and 3715.46 Å V II lines that confirmed the previous measurements of 2020. Subsequently, we performed a more accurate calculation using the procedure to calculate the Gaunt factors suggested by Sampson, obtaining results very close to the experimental values. These allowed us to assume that the calculations performed for 56 lines ranging between 3700 and 4600 Å (present in the photospheres of the Sun and the metal-poor star HD 8493), and without experimental information, are more accurate using the Gaunt factors proposed by Sampson. Read More
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