  Frequencies in oscillating $\beta$ Cephei stars are usually inferred by means
of radial velocities measured from the SiIII triplet 4552-4574 A. These lines,
relatively insensitive to the variation of Teff through a pulsation cycle, show
small equivalent width variations. In this study we aimed to verify if the
behavior of radial velocities and equivalent widths measured from other ions
are compatible with the one observed from SiIII lines and than to verify the
possible vertical stratification along the stellar atmosphere. For this reason
we selected from our spectra a number of, unblended and well isolated, CII, NII
and OII lines besides the famous SiIII triplet. All those lines cover the range
in optical depth between -2.1 and -0.5. Unfortunately, we did not find any
differences in the radial velocities behavior line-by-line and then we derived
the frequency of the principal radial mode combining all the velocities derived
from each spectral line separately. The inferred frequency was
f1=5.249677+/-0.000007 c/d.
  Another important task we would like to accomplish with this paper is to make
available to the community our large sample of spectroscopic data, that is 932
velocities and equivalent widths measured from our sample of C, N, O and Si
lines. All the spectra were acquired at the 1-meter class telescope of the
stellar station of the INAF - Osservatorio Astrofisico di Catania, in the
period starting from July, the 27th 2005 to November, the 1st 2006.
