Determine charge-transfer branching fractions

Determine the charge-transfer branching fractions from the effective YbAlO3 charge-transfer state to the selected ground and excited crystal-field manifolds, so that the electric-dipole matrix elements and the reverse-parametric-fluorescence sensitivity can be calculated without the equal-branch assumption.

Background

The magnitudes of the two electric-dipole matrix elements are inferred from the measured charge-transfer lifetime and assumed emission energies. Converting the lifetime into individual dipole magnitudes requires the branching fractions for decay to the ground and excited manifolds.

The benchmark assumes Bg=Bv=1/2 as an equal-branch reference. Since the actual branching fractions directly affect the effective dipole product and hence the predicted signal yield, their measurement is an unresolved material input.

References

The branching fractions in YbAlO3 are unknown, so we take B_g=B_v=1/2 as an equal-branch reference.

— Macroscopic Coherent Axion Production by Reverse Parametric Fluorescence  (2609.02150 - Bai et al., 2 Sep 2026) in Appendix, Section "Material and atomic-level reduction", subsection "Effective CT State and Electric-Dipole Input"