EXTENDING THE QUANTAL ADIABATIC THEOREM - GEOMETRY OF NONCYCLIC MOTION

We show that a noncyclic phase of geometric origin has to be included in the approximate adiabatic wave function. The adiabatic noncyclic ge ometric phase for systems exhibiting a conical intersection as well as for an Aharonov-Bohm situation is worked out in detail. A spin-1/2 ex periment to measure the adiabatic noncyclic geometric phase is discuss ed. We also analyze some misconceptions in the literature and textbook s concerning noncyclic geometric phases. (C) 1998 American Association of Physics Teachers.