Röntgen W.C. Röntgen The röntgen (R) is the old unit of exposure (X) and was expressed in statCoulomb (statC) per cubic centimeter (cm3) dry air. The unit is named after the German physicist Wilhelm Conrad Röntgen (1845 - 1923). 1 R = 2.58×10-4 coulomb (C) / kilogram (kg) 1 R corresponds to an absorbed dose of about 0.0088 Gy.
