IR and Raman spectra D 6530Distortion of the fcc lattice in Superstoichiometric β-YH 2+δ and Cubic YH 3-η Thin Films. -The metal insulator transition of Y films grown on CaF2 (111) substrates and capped with Pd are monitored by Raman spectroscopy. The Raman mapping image reveals the existence of the tetragonal YH2+δ phase between hcp YH3 and fcc YH2 during the unloading of the film. There is a regime of coexistence of YH2+δ and hexagonal YH3.The results are compared with measurements on Mg 0.1 Y 0.9 H x , which also shows a distortion of the cubic lattice. -(CARSTEANU*, A.-M.; RODE, M.; ZUR, D.; SCHOENES, J.; BORGSCHULTE, A.; WESTERWAAL, R.; J. Alloys Compd.