We start at this lower energy state and go up that means we need to absorb a photon, we have to take in energy.

我们从一个低能级开始，到一个高能级去,这意味着需要吸收一个光子，我们要获得能量。

麻省理工公开课 - 化学原理课程节选

And what we predict as an energy difference between two levels, we know should correspond to the energy of light that's either emitted, if we're giving off a photon, or that's absorbed if we're going to take on a photon and jump from a lower to a higher energy level.

我们预测，两个能级之间的能量差，我们知道，它要么和发出的光有关,如果它发出光子的话，要么它吸收光子,从低能级跃迁到，更高能级上去。

麻省理工公开课 - 化学原理课程节选