The paper proposes to use the discharge energy for the synthesis of chemically active particles in order to correct the shape and aspherize the surface of optical elements by reactive ion-beam etching. A stand was assembled on the basis of a radio frequency source of accelerated ions KLAN-105M, the design of which allows working with reactive gases. The possibility of increasing the etching rate of fused quartz by more than 5 times compared to ion etching with inert gases by creating a mixture of tetrafluoromethane (CF4) and argon (Ar) in a ratio of 1:1 is shown, while maintaining the initially smooth surface roughness ((sigmaeff~0.3 nm) in the range of spatial frequencies ν[5.0·10-2-6.4·101 μm-1]. Keywords: ion etching, reactive ion etching, roughness, surface, X-ray optics.