MOLECULAR-STATES OF O-2 CONFINED IN A CARBON NANOSPACE FROM THE LOW-TEMPERATURE MAGNETIC-SUSCEPTIBILITY

The magnetic susceptibility chi of O-2 adsorbed in micropores of activ ated carbon fibers (ACFs) having different micropore widths was measur ed at a wide temperature range of 1.7-100 K. The micropore structure o f ACF was determined by the analysis of the N-2 adsorption isotherm at 77 K. The adsorption isotherm of O-2 on ACF at 77 K was determined an d it was shown that O-2 is adsorbed in the micropore in a similar way to N-2 from the Dubinin-Radushkevich analysis of O-2 and N-2 adsorptio n isotherms. The chi-T relation suggested the presence of three kinds of O-2 molecular states in the micropore, that is, the isolated, the c luster, and condensed states; their stable region changes with the fra ctional filling and the temperature. Although the potential energy dif ference of the O-2-surface interaction of different pore systems is on ly 150 K by the potential calculation, the magnetic susceptibility mea surement can sufficiently evidence distinctly the presence of differen t states of O-2 molecules in the micropore.