When a photon of energy (E2​–E1​=hυ ) is incident on an atom in the ground state, the atom in the ground state E1​  may absorb the photon and jump to a higher energy state (E2​ ). This process is called stimulated absorption or induced absorption.Spontaneous absorption is the process by which an atom in its ground state spontaneously jumps to a higher energy state, resulting in the absorption of a photon. We do not have any process such as spontaneous absorption. This is because for absorption, we need to incident a photon of sufficient energy on the atom to stimulate the atom for absorption.