There are some advantages to employing such a methodology . Firstly, it is entirely analytical, and therefore technically exact, at least with respect to the quantum chemical information used to solve it. Second, vibrational mixing effects are included, which is very important in the case of low energy normal modes; these modes have been shown to mix upon electronic excitation. Thirdly, the entire vibrational continuum is taken into account as opposed to only the promoting mode. Fourthly, computing the rate in the time domain rather than the frequency domain is often computationally less expensive. Conversely, this method cannot be used accurately for internal conversion rate constants faster than 10 12 s -1 . However, there are also disadvantages to relying entirely on the lineshape. For example, Xu and co-workers noted that temperature effects were overtly broadening vibronic contributions in the spectral lineshape and width of some helicene derivatives, yielding a rate constant of < 34 s -1 , much smaller than should be expected.