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Frequencies in oscillating $\beta$ Cephei stars are usually inferred by meansof radial velocities measured from the SiIII triplet 4552-4574 A. These lines,relatively insensitive to the variation of Teff through a pulsation cycle, showsmall equivalent width variations. In this study we aimed to verify if thebehavior of radial velocities and equivalent widths measured from other ionsare compatible with the one observed from SiIII lines and than to verify thepossible vertical stratification along the stellar atmosphere. For this reasonwe selected from our spectra a number of, unblended and well isolated, CII, NIIand OII lines besides the famous SiIII triplet. All those lines cover the rangein optical depth between -2.1 and -0.5. Unfortunately, we did not find anydifferences in the radial velocities behavior line-by-line and then we derivedthe frequency of the principal radial mode combining all the velocities derivedfrom each spectral line separately. The inferred frequency wasf1=5.249677+/-0.7 c/d.  Another important task we would like to accomplish with this paper is to makeavailable to the community our large sample of spectroscopic data, that is 932velocities and equivalent widths measured from our sample of C, N, O and Silines. All the spectra were acquired at the 1-meter class telescope of thestellar station of the INAF - Osservatorio Astrofisico di Catania, in theperiod starting from July, the 27th 2005 to November, the 1st 2006.

Spectroscopy of the hot pulsating star Beta Cephei. Velocities and EWs from C,N,O and Si lines