NEA spectrum simulations are significantly more involved because they require a nuclear ensemble construction and electronic-structure calculations for each nuclear geometry in the ensemble. (We will discuss how to build the ensemble for fluorescence spectra in Section II.3.) Nonetheless, NEA spectra give absolute band shapes. Although the line half-width J is arbitrary, its value is chosen to be much narrower than the band width J. Thus, the band emerging from the NEA simulations reflects the actual band shape. Moreover, because the oscillator strengths are computed for every point in the ensemble, this approach includes information beyond the Condon approximation, recovering vibronic couplings.