Abstract. We find the maximal ideal spaces of a class of C*-algebras of pseudodifferential operators, called comparison algebras in [2], related to Schrödinger type expressions. This is achieved by constructing some multiplicative linear functionals explicitly, made possible by an improvement of a method of H. H. Sohrab. These algebras are useful in studying the Fredholm and spectral properties of partial differential operators (see [2]).

AMS Subject Classification (1991): 47F05, 35P99

Received November 5, 1997. (Registered under 3319/2009.)