A bi-convex solid immersion lens is disclosed, having a top and bottom convex surfaces. First and second regions of a second conductive type opposite to the first conductive type are provided in a surface of the semiconductor region in a predetermined interval. The comparison generally occurs automatically in response to the single query. A drive fluid andor an oxidizing fluid may be provided into the injection zone. The top surface of the oxide semiconductor film in the second region is in contact with a protective insulating film. It relates more particularly to the hydrocyanation of diolefins such as butadiene or of substituted olefins such as alkenenitriles, for instance pentenenitriles.