Side-hole to anti-hole conversion in time-resolved transient spectral hole-burning of emerald: ground state level versus excited state population storage in low magnetic fields

Abstract

Time-resolved transient spectral hole-burning experiments in zero field and in low magnetic fields B_∥c are reported for the chromium(III) R₁-line, 2Ā(²E) ← 2Ā(⁴A₂) of Chatham lab created emerald, Be₃Al₂Si₆O₁₈ ∶ Cr(III) (0.0017% per weight), in the temperature range of 3 to 12 K. In low magnetic fields and temperatures >5 K conversion of side-holes to anti-holes is observed with progressing time. Anti-holes are due to the population stored in ground state levels. The dynamics of the hole pattern can be well modelled by a set of coupled differential equations for the levels of the ⁴A₂ and ²E multiplets. The measurements allow the simultaneous determination of g-factors and spin–lattice relaxation rates in the excited state and the ground state. At 6 K the relaxation times between the split ±1/2 2Ā(²E) excited state levels and ±3/2 2Ā(⁴A₂) levels of the ground state are about 0.16 ms and 9 ms, respectively. From the temperature dependence it follows that the spin–lattice relaxation rates are dominated by Orbach processes in the experimental temperature range.