[en] The disclosure is concerned with exciplex dye lasers, i.e., lasers in which the emitting species is a complex formed only from a constituent in an electronically excited state. Noting that an exciplex laser, favorable from the standpoint of broad tunability, results from a broad shift in the peak emission wavelength for the exciplex relative to the unreacted species, a desirable class resulting in such broad shift is described. Preferred classes of laser media utilizing specified resonant molecules are set forth. (auth)

[en] A resonance radiationless energy transfer process has been found between the excited state of diphenylmethylene (a molecule with a triplet ground state) and fluorescein in a rigid alkaline glass at 77⁰K. By measuring the effect of fluorescein on the lifetime of excited diphenylmethylene, the critical transfer distance R₀ was found to be 61 A. This compares favorably with the theoretical value of 50 A calculated by the Forster weak-interaction dipole treatment. This is the first example of the dipole-allowed radiationless energy transfer of the type ³D* + ¹A → ³D + ¹A*. 3 figures