A 2-DIMENSIONAL QUANTUM CRYSTAL - H-2 ON NACL(100)

Monolayers of H-2 On NaCl(100) at 5.2 K have been prepared from both n ormal and pam-enriched hydrogen and examined by polarized infrared spe ctroscopy. Vibrational features associated with J=0 and J=1 molecules are distinguished. The spectroscopic data are consistent with hydrogen adsorbed to two distinct sites: surface Na+ ions and Cl- ions. For th e pam-enriched sample a two-dimensional crystal structure is proposed in which J=0 molecules reside on Nat ions and J =1 molecules cover Cl- sites. The polarization measurements show that all transition dipoles are perpendicular to the NaCl(100) surface. The mechanism for the inf rared absorption is through electric field induced transition dipoles. (C) 1998 American Institute of Physics.