The results of a heat-capacity study of the region between one and two layers in the Kr/graphite (Grafoil) system are presented. Heat-capacity anomalies corresponding to the commensurable-incommensurable transition, the commensurable-fluid transition, and a previously unobserved incommensurable-fluid transition delimit the high-coverage extent of the registered phase. A phase diagram proposed on the basis of the heat-capacity data suggests the possibility of a new type of multicritical point.

• Received 4 December 1979

DOI:https://doi.org/10.1103/PhysRevLett.44.466