$$k_r=2.88\times10^{-9}n^2\langle\tilde{v}\rangle_\text{av}^2 \int\varepsilon_{\tilde{v}}d\tilde{v}$$
$$f=4.32\times10^{-9}\int\varepsilon_{\tilde{v}}d\tilde{v}$$
I plan to use the above equations to calculate the lifetime $k_r$ of a fluorescent molecule. I need to calculate the oscillator strength $f$ in the 2nd equation, but I don't understand how to use the equation used to calculate the oscillator strength.