We study the interaction of a small number of resonant two-level atoms in a cavity coupled to a quasi-continuum of cavity modes. During the interaction we induce externally a phase step to one of the atoms. As a result an enhancement in the photon emission to the field is observed. The phase step is obtained by a pulse which causes the atom to be off-resonance for a short time interval. The effect is strongest in cases where the number of atoms is small. The enhancement is not restricted to a small parameter range but should be observable in many systems even though the φ phase shift gives the best enhancement.