The effect of pressure on energy transfer in Cr3+:Tm3+:YAG has been co
nsidered. We find that pressure increases the separation in energy of
the 4T2 and 2E levels of Cr3+ and that this increase leads to both an
increase in Cr3+ --> Tm3+ energy transfer efficiency and a decrease in
Cr3+ --> Tm3+ energy transfer rate. We attribute the increase in tran
sfer efficiency to a reduction in the spin-orbit coupling of the 4T2 a
nd 2E levels with increasing pressure and the decrease in transfer rat
e to the elimination of the thermal population of the 4T2 level. We in
clude a discussion of the relationship of effects of pressure and temp
erature on the energy transfer properties of Cr3+.