Experimental
Bare DPBBTD and its vdW complexes with Xe atoms were prepared in supersonic free jets. Gaseous DPBBTD was generated by heating the solid to ca. 423 K and the vapour was expanded into a vacuum chamber through a 150 µm cw-nozzle, with a Ne buffer gas of ca. 760 Torr. For the vdW complexes, the Ne gas was replaced with Xe gas. The exciting laser (Lambda Physik LPX105 + FL3002) beam crossed the supersonic jet at 7 mm downstream of the nozzle. The laser line width was estimated to be less than 0.6 cm−1 by the spectral bandwidths observed in the present study. The temporal width of the laser pulse was ca. 10 ns. In the measurement of LIF excitation spectra, the intensity of the fluorescence signal was recorded continuously as the laser wavelength was scanned. The fluorescence decay curves were recorded on a digital oscilloscope.
