They were using the laser to excite and ionize the atoms liberated by the heat of the flame in order to measure the characteristic emissions of different flames.
当时他们用这种激光来激发并电离那些被火焰的高温裂解出来的原子，目的是测量不同火焰的特征辐射。
2
But what they noticed was that even when they turned the flame off they were still getting a signal - in other words, the laser was breaking up as well as exciting the oxygen.