A He⁺ ion in its ground state is fired toward a hydrogen atom in its ground state and at rest. Find the minimum kinetic energy, in eV, of the He⁺ ion so that both one-electron species can be excited.
Physics · Atomic Structure and X-rays
JEE Mains Advanced

Question

A He⁺ ion in its ground state is fired toward a hydrogen atom in its ground state and at rest. Find the minimum kinetic energy, in eV, of the He⁺ ion so that both one-electron species can be excited.

Physics · Atomic Structure and X-rays

G1 Physics · Accepted Answer

The first excitation energies are 10.2 eV for H and 40.8 eV for He⁺. Including two-body collision kinematics and requiring both species to be excitable gives the minimum projectile energy 255 eV.