SPECTRAL HOLE-BURNING ON SILICON PHTHALOCYANINES ISOLATED IN AN ARGONMATRIX

Irradiation of the monomeric phthalocyanine HexSiO(SiPc)OSiHex3 isolat ed in an Ar matrix at T = 13 K with the 632.8 nm line of a He/Ne laser produces a resonant spectral hole in the vibrational sideband located about 700 cm-1 above the origin of the Q band. This hole is accompani ed by several sideholes in the origin region. These permit a precise d etermination of several excited-state vibrational frequencies. For dim eric Hex3SiO(SiPC-O-SiPc)OSiHex3 in the same matrix the changes in the absorption spectra after irradiation into the Q band reveal an out-of -plane polarization of the bands which are not present in the monomer absorption. This points to substantial charge-resonance contributions to the excitonic coupling between the two SiPc units in dimeric Hex3Si O(SiPc-O-SiPc)OSiHex3.