We present an analysis of high time resolution spectra of the chemically peculiar Ap star HD 213637 .
The star shows rapid radial velocity variations with a period close to the photometric pulsation period .
Radial velocity pulsation amplitudes vary significantly for different rare earth elements .
The highest pulsation amplitudes belong to lines of Tb iii ( \sim 360 m s ^ { -1 } ) , Pr ii ( \sim 250 m s ^ { -1 } ) and Pr iii ( \sim 230 m s ^ { -1 } ) .
We did not detect any pulsations from spectral lines of Eu ii and in H \alpha , in contrast to many other roAp stars .
We also did not find radial velocity pulsations using spectral lines of other chemical elements , including Mg , Si , Ca , Sc , Cr , Fe , Ni , Y and Ba .
There are phase shifts between the maxima of pulsation amplitudes of different rare earth elements and ions , which is evidence of an outwardly running magneto-acoustic wave propagating through the upper stellar atmosphere .