Comparison of Se I–IV expansion opacity at T = 10 000 K calculated with the three different sets of atomic data. Each banner corresponds to the expansion opacity calculated with the specific set of atomic data. In the top panel the opacity is calculated considering Se I–IV data from this work. In the middle panel the opacity is calculated considering Se I–IV data from Model I. In the bottom panel the opacity is calculated considering Se I–IV data from model ‘Tanaka+,2020’. In the plot legend, the notation ‘I–II’, ‘I–III’, and ‘I–IV’ indicates that the opacity is calculated by including time-by-time additional ionisation states.