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| if <0: log γ,,6,, in units of 1/(s*N,,H,,) at l0000 K (where N,,H,, is the number density of neutral Hydrogen atoms in 1/cm^3^); | if <0: log γ,,6,, in units of rad/(s·N,,H,,) at l0000 K (where N,,H,, is the number density of neutral Hydrogen atoms in 1/cm^3^); |
van der Waals damping parameter describes broadening of spectral lines due collisions with neutral particles, e.g. Hydrogen atoms. In VALD3 it can have three values:
if 0: it is not known;
if <0: log γ6 in units of rad/(s·NH) at l0000 K (where NH is the number density of neutral Hydrogen atoms in 1/cm3);
if >0 : two parameters as defined in Barklem et al. 2000A&AS..142..467. Integer part is cross-section σ, fractional part is velocity parameter α.