On the Branching in the Emission Relations of Ca II lines in Solar   Prominences
  We observe simultaneously the Ca II K, Ca II 8542 and H-beta emissions in solar prominences at high spatial and spectral resolution. We confirm a branching in the emission relations of Ca II and H-beta. This is related to non-thermal line broadening, which affects the Ca II lines much more than H-beta. The classical non-thermal (Maxwell) line broadening, determined by comparison of the width of hydrogen lines with those from calcium lines, is not sufficient to explain the Ca II widths. This indicates an additional broadening by large-scale motions of the unresolved prominence fine-structure. 
G. Stellmacher and E. Wiehr
astro-ph.SR