Asymmetric profiles of Ca I lines belonging to the transitions n1F°3 → 31D2 observed in long laser spark

This study aimed to determine the Stark broadening parameters of asymmetric profiles for Ca I lines within the singlet transitions [4,5f] 1F degrees 3 -> [3d4s] 1D2. To improve the signal-to-noise ratio of the measurements, a long laser plasma, also known as "long spark", was utilized as a plasma source. Compared to common spherical plasma, long plasma is more homogeneous and illuminates a larger area in the focal plane of the spectrograph, resulting in a 5-7 fold increase in the vertical dimension of the plasma image on the detector. Therefore, the use of long laser plasma is more appropriate for determining the Stark parameters. The electronic density was determined using Mg I lines with known electron-impact shift and width, while the plasma temperature was determined using Fe I lines within the 368-375 nm range. The temperature and electron density were varied within the range of 3500-10,000 K and (1-16) x 1016 cm-3. The profile distortion caused by Doppler, resonance, and van der Waals broadening mechanisms were considered and found to have no significant influence on the studied lines. The determined electron-impact parameters are precise within 25%, and the ion parameter's contribution for the 435 nm line is substantially higher than that for the 487 nm line.