Third Order Contributions to SpinForbidden Rare Earth Optical Transition Intensities.
Abstract
Quantitative calculations show that numerous parity  and spinforbidden linear optical transitions observed in trivalent rare earth ions acquire a major fraction of their intensity from hitherto neglected contributions involving spinorbit linkages within excited configurations. Motivated by the importance of analogous linkages previously demonstrated in twophoton absorption, a general expression for these new "third order" terms, applicable for all 1^ {N}to 1^{N} transitions, is incorporated into a revised Judd Ofelt analysis of observed intensities. Presenting this revised analysis of observed linear absorption intensities in aqueous solution for the entire trivalent lanthanide series, we show that these new contributions are important throughout the lanthanides, and selectively modify spinforbidden DeltaS = 1 transitions over spinallowed DeltaS = 0 transitions. With substantial modification of previously fitted phenomenological parameters, the overall fit to observed intensities is somewhat improved. Particular improvement has been achieved in understanding selected individual transitions, such as the ^4I _{9/2} to ^2rm F_{5/2} transition in Nd^{3+} , the ^6rm H_{5/2 } to ^4 rm H_{7/2} transition of Sm^{3+} and the ^8rm S_{7/2} to ^6rm P_{3/2 } transition of Gd^{3+ }. However, many important predictions of this new analysis could not be confirmed due to the lack of the experimental resolution. Important predictions which could not be spectrally resolved in aqueous solution include the large third order cancellations of respective second order terms in the ^6rm H_ {5/2} to ^4rm D_{1/2} transition of Sm^{3+}, the ^7rm F_6 to ^5rm D_{3,2,1,0} transitions of Tb^{3+} and the ^6rm H_{15/2 } to ^4 (M, I)_{15/2}, ^4rm F_{5/2} transitions of Dy^{3+}. Other unresolved transitions with dominant third order terms are the ^6rm H_{5/2} to ^4rm H_{9/2,11/2} transitions of Sm ^{3+}, the ^6 rm H_{15/2} to ^4rm M_{17/2} , transitions of Dy^{3+} and the ^5rm I_8 to ^3rm I_ 7 transition of Ho^{3+} . In addition, we extend this analysis to selected trivalent actinides. Other extensions examined include the possibility of gorbital contributions and contributions involving the linear crystal field for selected hypersensitive transitions, in particular the ^7rm F_0 to ^5 rm D_0 transition of Eu^ {3+}.
 Publication:

Ph.D. Thesis
 Pub Date:
 1991
 Bibcode:
 1991PhDT.......231B
 Keywords:

 Physics: Optics; Physics: Atomic; Physics: Molecular