where ⊿νis the linewidth, in frequency units, of the transition from the excited to the ground state. As the ground state has an infinite lifetime and therefore represents a so-called δ-function (infinitely narrow peak), the width immediately mirrors the width of the excited state.
However, the mearsured linewidth is always greater than the actual linewidth, which is derived from the natural lifetime.
We have to take into account a further broadening of the linewidth, i.e., a reduction in the lifetime, by collision, stimulated emission(as in lasers, cf. section3.4.5) or by Doppler shift as caused by the relative motion of the molecules and the observer. Broadening of the linewidth by collision and induced emission, as homogeneous processes, lead to a Lorentzian shape, while Doppler broadening, as an inhomogeneous process, yields a Gaussian line shape. The combination of both line shapes is described by the so-called ‘Voigt’ profile.
第二个单词是 ⊿v
大家不要看错了
多谢了
不要翻译器翻译的