The experimental spectrum of neutral BrBz, presented in Figure (a), is obtained from A = 𝑙𝑜𝑔 (𝐼without Bz / 𝐼with Bz), where 𝐼without Bz and 𝐼with Bz are the transmitted signal of the broadband x-ray flux without BrBz molecules in the interaction region and with flow of BrBz molecules at room temperature, respectively, as described in detail previously. The spectrum matches well with previously reported results, and it agrees with our calculations, shown in red in Figure . The spectrum exhibits one dominant peak at 285.1 eV, labeled as A in Figure (a), followed by at least 4 discernable peaks of lower intensity, labelled B-E. In accordance with the previous work, we assign peak A as due to transitions from the 1sC orbitals (i.e., the 1s orbitals of the C atoms not bound to Br atom) to the two lowest unoccupied π* molecular orbitals, similar to the 1sC→π* transition observed at 285.25 eV in the x-ray spectrum of Bz. 9,10,13,15 (See Table for details on the peak assignments and calculated energies).