Fig. 1. Mass spectra of boron oxide cation clusters in the m/z range of 40–250 produced by pulsed laser vaporization of a ¹⁰B-depleted boron target in the expansion of (a) helium seeded with 1% O₂ (red line), and (b) helium seeded with 10% argon and 1% O₂ (black line).