@D01801-1@ occurring by @T06531@ from a 'bound' to an 'unbound' vibronic state. In an @A00043@ of a molecular entity, the appearance of a diffuse band region within a series of sharp bands is called predissociation, since @I03255@ with frequencies within the diffuse region leads to effective @D01801-2@. The energy of the band is smaller than that of the @D01801-2@ continuum of the bound state.