Recent Hermes measurements are presented on the coherent and incoherent part of the cross section for the exclusive diffractive production of \rho ⁰ mesons. Based on data taken with a variety of targets, ¹H, ²H,³He,¹⁴N, ²⁰Ne and ⁸⁴Kr, the method to extract the coherent to incoherent cross section ratios as a function of coherence length l_coh and momentum transfer Q² will be presented. The measurement of those ratios could contribute to the study of how quark--antiquark pairs interact with the nuclear medium. Using the ¹H and ¹⁴N targets, the nuclear transparency of \rho ⁰ production has been measured as a function of coherence length. The data have been analysed to search for a possible onset of color transparency and are compared with recent theoretical calculations.

PACS numbers: 13.60.Le