Momentum-transfer scaling in hydrogen-isotope collision systems

The differential cross sections for excitation of atomic hydrogen isotopes to their $n=2\mathrm{}$ states by proton or deutron impact are found to follow a simple scaling relationship. The momentum-transfer-scaled differential excitation cross sections, for a projectile velocity of 1.26 a.u., produce one differential cross-section curve for all four possible hydrogen-isotope collision systems. The experimental results are in excellent agreement with our Glauber-approximation calculations.