Nuclear magnetic resonance and relaxation in vitreous and liquid ${\mathrm{B}}_2$${\mathrm{O}}_3$ and ${\mathrm{B}}_2$${\mathrm{S}}_3$

The vitreous and liquid phases of ${\mathrm{B}}_2$ ${\mathrm{O}}_3$ and ${\mathrm{B}}_2$ ${\mathrm{S}}_3$ are investigated by the techniques of continuous-wave and pulsed nuclear magnetic resonance. The temperature dependence of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ line shape and spin-lattice relaxation rate are studied up to 650°C for ${\mathrm{B}}_2$ ${\mathrm{O}}_3$ and 250°C for ${\mathrm{B}}_2$ ${\mathrm{S}}_3$. A structural model involving the progressive fragmentation with increasing temperature of the linked network structure, which exists at ambient temperatures, is advocated for both glasses.