In the context of @R05063@, the integral, \(J=\int _{0}^{\infty }f_{\text{D}}^{'}\left(\sigma \right)\ ɛ_{\text{A}}\left(\sigma \right) \ \mathrm{d}\sigma \), which measures the overlap of the @E02060@ of the excited donor, D, and the @A00043@ of the @G02704@ acceptor, A; \(f_{\text{D}}^{'}\) is the measured normalized emission of D, \(f_{\text{D}}^{'}=\frac{f_{\text{D}}\left(\sigma \right)}{\int _{0}^{\infty }f_{\text{D}}\left(\sigma \right) \ \mathrm{d}\sigma }\), \(f_{\text{D}}(\sigma)\) is the @P04631@ of the donor at wavenumber \(\sigma \), and \(ɛ_{\text{A}}(\sigma)\) is the decadic @M03972@ of A at wavenumber \(\sigma \). In the context of @F02488@, \(J\) is given by: \[J=\int _{0}^{\infty }\frac{f_{\text{D}}^{'}\left(\sigma \right)\ ɛ_{\text{A}}\left(\sigma \right)}{\sigma ^{4}} \ \mathrm{d}\sigma \] In the context of @D01654@, \(J\) is given by: \[J=\int _{0}^{\infty }f_{\text{D}}\left(\sigma \right)\ ɛ_{\text{A}}\left(\sigma \right) \ \mathrm{d}\sigma \] In this case \(f_{\text{D}}\) and \(ɛ_{\text{A}}\), the @E02060@ of donor and @A00043@ of acceptor, respectively, are both normalized to unity, so that the @O04322@ for energy transfer, \(k_{\text{ET}}\), is independent of the @O04339@ of both transitions (contrast to Förster mechanism).