The mixed crystal absorption spectra of 1,1′-diethyl-2,2′-cyanine iodide

Solvent, Temperature, and Excitonic Effects in the Optical Spectra of Pseudoisocyanine Monomer and J-Aggregates

“…This matrix shift has been taken into account phenomenologically in the theory of molecular excitons. , The energy down shift results largely from the dispersive stabilization of the S 1 state relative to the ground state owing to the higher polarizability of the former. In neat PIC the solvent shift must be close to that in aza-PIC, since the resonance interaction leads to a nearly symmetric level splitting by 1270 ± 10 cm -1 relative to the monomer peak at 18223 cm -1 in the aza-PIC crystal .…”

“…Fairly large Stokes' shift between the fluorescence and absorption band maxima of monomeric PIC in 50% glycerol/water glass (570 cm -1 , Figure ) reveals strong coupling to low-frequency vibrations. A weak ZPL of PIC monomer in the aza-PIC matrix is accompanied by a huge asymmetric wing spreading between 40 and 340 cm -1 (at half-intensity) and peaking at 100 ± 10 cm -1 (data taken from Figure in ref ). These vibrations seem to be characteristic mainly to the chromophore itself rather than to the matrix, because the Stokes' shift in a glass is twice as large as the width of the wing in the crystal (300 cm -1 ).…”

“…PIC iodide embedded in a single crystal of 1,1‘-diethyl-9-aza-2,2‘-cyanine iodide (aza-PIC) shows the strongest zero-phonon line at 18 223 cm -1 (548.77 ± 0.05 nm) at 1.8 K …”

“…Bands belonging to upper excitonic transition are shown also in an enlarged scale (5×). Vertical bars indicate the positions of zero-phonon lines of PIC impurity in aza-PIC crystal at 548.77, 552.6, and 555.75 nm from ref . Position of the 0−0 origin of PIC monomer in vacuum is shown with a dotted bar.

4 Temperature dependence of the PIC aggregate absorption in 50% glycerol/water glass: (a) J-band of the blue form in the presence of 2 M KCl in a 10 μm cell, absorption level outside the band was set to zero; (b) J-band of the red form in the presence of 4 M KF in a 10 μm cell, (c) the same for the upper exciton bands in a 100 μm cell.

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“…Bands belonging to upper excitonic transition are shown also in an enlarged scale (5×). Vertical bars indicate the positions of zero-phonon lines of PIC impurity in aza-PIC crystal at 548.77, 552.6, and 555.75 nm from ref . Position of the 0−0 origin of PIC monomer in vacuum is shown with a dotted bar.…”