Whenever I want to calculate a Raman spectrum, my quantum chemical programs give me Raman scattering activities. As the common Raman spectrum is dependent on the incident wavelength of the used laser this seems quite logic, because the program cannot guess which laser the experimentalists could have used.
At least in Gaussian 09, for some methods, there is the possibility to calculate the Raman scattering activities for a certain incident light frequency through cphf=rdfreq.
As far as I know, the latter would give me the dynamic Raman activities and whenever I don't enter the incident light frequency I will get static Raman activities.
To get the intensities out of the activities, I was given the following equation, which I was told only holds for the dynamic activies: $$I_k \varpropto \frac{S_k}{\tilde{\nu}_k} \frac{\left(\tilde{\nu}_\text{in} - \tilde{\nu}_k\right)^4}{1-\exp\left(-\frac{h c \tilde{\nu}_k}{k_B T}\right)} $$
But what if the calculation method that I use is not able to produce dynamic Raman activities (i.e. because it's not implemented) and I am only able to get those static Raman activities? How do I get Raman intensities from them?