Contact and bulk electromodulated transmission spectra of blue bronze

We have used electromodulated infrared transmission spectroscopy to search for states associated with soliton excitations of the CDW phase in blue bro nze with tunable diode lasers. in particular, we have searched the spectral region near the edge of the CDW gap and compared the spectra associated wi th contact polarization (i.e. current injection) with that associated with hulk CDW polarization. No new states are observed, implying that the lifeti me of injected solitons is < 0.5 mu s. Both bulk and contact polarization a re observed to shift the frequency of high energy phonons, suggesting that the density of electronic :states in the gap, present because of CDW fluctu ations, depends on CDW polarization.