dobâr-, dv-, dotâyi
Fr.: double, à ~
dobâr yonidé (#)
Fr.: deux fois ionisé
An atom that has lost two of its external electrons, for example O++ ([O III]).
doubly refracting crystal
bolur-e šakst-e dotâyi
Fr.: cristal à double réfraction
A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.