The gas absorption cell for GIANO-TNG

GIANO is an high resolution cross-dispersed spectrometer operating at near IR wavelengths (0.9-2.5 microns). One of its primary aims is to measure radial velocities of cool stars with an accuracy of a few m/sec. To this purpose, the spectrometer requires a gas absorption cell which should ideally produce several hundreds of measurable lines distributed over the whole wavelengths range. We show that this can be conveniently achived using a combination of halogen hydrates, namely HCl, HBr and HI. We present and discuss the design and development of such a cell.