The shape and amplitude of the X emission spectra were found to depend on the experimental temperature (110-280 K). The presence of an isoemissive point in the temperature-dependent emission spectra suggests the presence of two emitting species. Since the emission spectra are independent of the excitation wavelength, at least one of these species must be formed through an excited-state process. In addition, the time resolved emission spectra of the X films change with time, shifting towards longer emission wavelengths as time increases. These results are consistent with the presence of both a locally excited state and an excimer. No rise time is observed for the excimer emission decay, which suggests the presence of pre-formed excimers.