RAMAN SPECTRA OF SOLID MOLECULAR NITROGEN

($^{\ast}$) Laboratoire d'Infrarouge, Associ\'e au CNRS, B$\hat{a}t.$ 350, Universit\'e Paris XI, 91405 ORSAY-C\'edex, FRANCE. ($^{\ast\ast}$) Dept. of Physics, Ohio State University, 174 West, 18th Avenue, Columbus Ohio, 43210, USA. ($^{\ast\ast\ast}$) Dept. of Physics and Astronomy, The University of Alabama, Tuscaloosa Alabama, 35487, USA.Author Institution: Laboratoire d'Infrarouge, Associ\'e CNRS, B$\hat{a}t$ 350, Universit\'e; Dept. of Physics, Ohio State University; Dept. of Physics and Astronomy, The University of AlabamaDue to the simpler geometrical arrangement, the theoretical interpretation of molecular interactions may be easier in the lattice than in the gas phase. In the case of the nitrogen molecule, the structure of the solid at normal pressure is known. A phase transition occurs at a temperature $T_{ph} = 35.6K$. The crystal is cubic $(\alpha-N_{2}$ ) for $T T_{ph}$. This paper reports preliminary results of a Raman scattering study on single crystal $N_{2}$. The experiment is specifically designed to investigate the effect of the above structural phase transition on the molecular and phonon excitations. The crystal $(4\times 2 \times 2 cm)$ is grown in a cryostat where the temperature is servo controlled over a large domain by appropriate heating of a flow of gaseous helium. The spectra are excited with a krypton laser and the scattered beam recorded with a spectral resolution equal to about $1 cm^{-1}$. The crystal cell, the optical system to enhance the signal to noise ratio and the growth technique are also described