We report results on the electrodynamic response of TiOCl, a
low-dimensional spin-1/2 quantum magnet that shows a spin gap formation
for T<T-c1 = 67 K. The Fano-like shape of a few selected, infrared
active phonons suggests an interaction between lattice vibrations and a
continuum of low-frequency (spin) excitations. The temperature
dependence of the phonon mode parameters extends over a broad
temperature range well above T-c1, indicating the presence of an
extended fluctuation regime. In the temperature interval between 200 K
and T-c1, there is a progressive dimensionality crossover (from two to
one), as well as a spectral weight shift from low towards high
frequencies. This allows us to identify a characteristic energy scale
of about 430 K, ascribed to a pseudo-spin-gap.</textarea>
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