The fluctuation spectrum responsible for the inelastic scattering in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6.99},$ which was recently determined from consideration of the in-plane optical conductivity in the infrared, is used to calculate the temperature dependence of the microwave conductivity at several measured frequencies. Reasonable overall agreement can only be achieved if, in addition, some impurity scattering is included within a model potential intermediate between weak (Born) and strong (unitary) limit.

• Received 20 August 2001

DOI:https://doi.org/10.1103/PhysRevB.65.064514