| Abstract: | We examine and compare the sensitivity of selected Ba II, Fe I, Fe II, Ni I,
and Cr I spectral lines to changes of the line-of-sight velocity by
sharpness of their line profiles and response functions to line-of-sight
velocity evaluated by the 1-D model of the quiet solar atmosphere in the LTE
approximation. The set of selected lines includes the Ba II 4554 A line,
generally considered to be an excellent Doppler mapper. Our findings
confirm earlier results showing that the sensitivity increases not only with
wavelength, as anticipated from the Doppler relation, but mainly with the
sharpness of line profiles given by the ratio of their depths and widths.
The line Fe I 5247 A is the most sensitive in our set whereas the Fe I and
Fe II infrared lines show very low sensitivity because of their large
thermal widths. The line Ba II 4554 A shows only moderate sensitivity due
to its large width given by broad hyperfine structure and isotopic split.
For the first time we identify a very promising and so far unknown Doppler
mapper of the solar photosphere and low chromosphere, which is the line Ba
II 6497 A. Its sensitivity is comparable with the sensitivity of Fe I 5247 A
and lines used in the helioseismology and clearly surpasses the
sensitivity of Ba II 4554 A. The line Ba II 6497 A offers many advantages
making it a highly recommendable choice for future dedicated studies of
line-of-sight velocities in the photosphere and low chromosphere and
possibly for helioseismology investigations. |