Abstract
The author obtains simple analytical expressions for the cross sections of the state-changing and ionisation collisions of Rydberg atoms with neutral atomic particles due to the Rydberg-electron-perturber interaction. The theoretical investigation is based on the impulse approximation and binary encounter approach for the form factor. The earlier results of Alekseev and Sobel'man (1965) and Omont (1977) turn out to be the limiting cases of the author's expressions. The calculated quenching cross sections for the Rydberg states agree well with experimental results and numerical calculations.