The figure shows a scheme for extracting negative hydrogen ions from a particle beam. Grids 1 and 4 are grounded. A negative potential is applied to the tube with grids 2, 3. Grid 2 draws protons from the hydrogen plasma, which is located behind grid 1. The tube is filled with gas. Protons passing through the gas are partly converted into neutral hydrogen atoms H0, and partly into H−-ions. Determine at what angle to the tube axis the H−-ions will move behind grid 4, if the angle between the planes of grids 3, 4 and the tube axis is α.