When the laser intensity and pulse duration are fixed, with the increase of vibrational quantum number, the multi-photon resonance transition frequency becomes smaller, which is consistent with the energy level distribution of non-harmonic oscillator. 当激光的强度和脉冲持续时间一定时,随着振动能级的升高,各级多光子共振跃迁的频率越来越小,说明了能级间隔越来越密,这与非谐振子的能级分布相吻合。