LASER-INDUCED EMISSION-SPECTROSCOPY OF MATRIX-ISOLATED CARBON MOLECULES - EXPERIMENTAL SETUP AND NEW RESULTS ON C-3

We have studied small carbon molecules using a matrix-isolation techni que. Our experimental setup is described in detail. The carbon cluster s were produced by evaporating graphite and trapping the carbon-vapor molecules in solid argon, where molecular growth could be induced by c ontrolled matrix annealing. To identify the produced molecules, absorp tion spectroscopy in the ultraviolet (UV)-visible and infrared (IR) sp ectral ranges was applied. Additional characterization of the excited and ground states of the molecules was obtained from emission and exci tation spectra. The molecules were excited by a pulsed dye laser syste m and the emission spectra were recorded with a high-sensitivity photo diode-array spectrometer. We present our measurements on linear C-3. T he (A) over tilde (IIu)-I-1 excited state of linear C-3 was populated by the electronic transition (A) over tilde (IIu <--)-I-1(X) over tild e (1)Sigma(g)(+), and the corresponding excitation spectra of the C-3 fluorescence ((A) over tilde (IIu)-I-1 -->(X) over tilde (1)Sigma(g)()) and phosphorescence ((a) over tilde (IIu)-I-3-->(X) over tilde (1)S igma(g)(+)) were studied. Comparison of excitation and absorption spec tra 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 l ifetime of the (A) over tilde (IIu)-I-1 excited state of C-3 in solid argon was found to be shorter than 10 ns. The phosphorescence transiti on (a) over tilde (3)IIu-->(X) over tilde (1)Sigma(g)(+) decays in abo ut Id ms and its rise indicates fast vibrational relaxation within the triplet system. Our data support a linear ground state geometry for C 3 also in solid argon. (C) 1998 American Institute of Physics.