Nonexponential photon-echo decays of paramagnetic ions in the superhyperfine limit

Nonexponential photon-echo decays are observed in ruby, Er3+, and Er3+ with samples of low ion concentrations in high (10-50 kG) magnetic fields. At the highest fields, photon-echo decays are field independent and their temporal forms are identical for all three systems. This behavior is attributed to optical dephasing arising from electron-spin nuclear-spin superhyperfine interactions in the presence of a frozen core. © 1991 The American Physical Society.