Laser-induced emission spectroscopy of matrix-isolated carbon molecules: Experimental setup and new results on C3

We have studied small carbon molecules using a matrix-isolation technique. Our experimental setup is described in detail. The carbon clusters were produced by evaporating graphite and trapping the carbon-vapor molecules in solid argon, where molecular growth could be induced by controlled matrix annealing. To identify the produced molecules, absorption spectroscopy in the ultraviolet (UV)-visible and infrared (IR) spectral ranges was applied. Additional characterization of the excited and ground states of the molecules was obtained from emission and excitation spectra. The molecules were excited by a pulsed dye laser system and the emission spectra were recorded with a high-sensitivity photodiode-array spectrometer. We present our measurements on linear C3. The à 1Πu excited state of linear C3 was populated by the electronic transition à 1Πu←X̃ 1Σg+, and the corresponding excitation spectra of the C3 fluorescence (à 1Πu→X̃ 1Σg+) and phosphorescence (ã 3Πu→X̃ 1Σg+) were studied. Comparison of excitation and absorption spectra yielded information on site effects due to the matrix environment. Emission bands in the fluorescence and phosphorescence spectra up to vibrational energies of 8500 cm−1 could be observed. The radiation lifetime of the à 1Πu excited state of C3 in solid argon was found to be shorter than 10 ns. The phosphorescence transition ã 3Πu→X̃ 1Σg+ decays in about 10 ms and its rise indicates fast vibrational relaxation within the triplet system. Our data support a linear ground state geometry for C3 also in solid argon.