Infrared investigation of field induced SDW formation in bechgaard salts.

Summary form only given. We report on microwave and far infrared spectroscopic measurements on (TMTSF)/sub 2/ClO/sub 4/ taken at various magnetic fields and temperatures, covering a substantial part of the phase diagram of this quasi one-dimensional organic conductor. The data taken at monochromatic energies versus magnetic field at various temperatures show steps in the optical signal, which follow closely the established phase diagram. Spectroscopic measurements reveal a SDW gap at 14 cm/sup -1/ which is equal in all subphases and independent of magnetic field and temperature. Moreover, we found a sharp mode at 2.4 cm/sup -1/ which can be identified as a strongly pinned, collective excitation of the condensate. Finally, we observed two phonon features at 17 cm/sup -1/ and at 31 cm/sup -1/ which renormalise when the SDW state is entered. The latter two observations indicate an unexpected, strong coupling between the condensate and the underlying lattice.