The S1-S0 oscillator strengths of the CBN_1-m and CBN_2-m series obtained with the ADC(2) method are listed in Table and are displayed in Fig. ). While the S1-S0 oscillator strength is very low for small m, it increases approximately linearly with the number of units, as expected from the Thomas-Reiche-Kuhn sum rule. The CBN_2-m oscillator strengths are systematically larger than those of the CBN_1 series.