Fig 1

1. Electronic Raman Effect of Cr3+ in Ruby (Al203: Cr3+): Raman Electronic Paramagnetic Resonance of the ground and excited states of the R1 emission. Anant K. Ramdas, Purdue University, DMR 0705793 Research goal:To discover and delineate electronic Raman effect of the ground state of paramagnetic impurities in insulators and semiconductors subjected to an external magnetic field. The focus in this investigation is on the Cr3+ impurities in corundum, Al203, i.e. ruby, and explore Resonance Raman effect of the transitions within the Zeeman multiplet of the ground state of Cr3+. We have successfully observed the Raman effect of the electronic ground state of Cr3+ in ruby where Cr3+ ions partially replace randomly the Al3+ ions of Al203. The ground state is the 4A2 four fold degenerate final state of the R1 emission of ruby which splits into, +3/2,1/2, -1/2, and -3/2 levels in an external magnetic field B along ĉ, the optic axis of ruby; the R1 photoluminescence (PL) then displays the six components (Pl2-Pl7) at 6T shown in the upper part of Fig. 1. Employing a tunable ring laser, operated with DCM dye excited with the 5145 Å line of the Ar+ laser, the Raman-electron-paramagnetic (Raman-EPR) of Cr3+ has been observed for the first time. (Lower half of Fig. 1). The resonantly enhanced Raman-EPR features are displayed in Fig. 2. The spectacular resonant enhancement occurs as a consequence of the simultaneous fulfillment of the resonance conditions for both the exciting laser (ħωL)and the Raman shifted scattered (ħωs) photons, shown in the two insets of Fig. 2. These observations provide several examples of the such doubly enhanced Raman-EPR transitions, some in the anti-Stokes Raman spectrum, some in the Stokes, and some in both. These illustrate in a particularly graphic fashion the microscopic mechanism contemplated in the Kramers-Heisenberg theory for the Raman effect. Fig 1

2. Electronic Raman Effect of Cr3+ in Ruby (Al203: Cr3+): Raman Electronic Paramagnetic Resonance of the ground and excited states of the R1 emission. Anant K. Ramdas, Purdue University, DMR 0705793 Doubly Resonant Raman-EPR Future Plans:The novel results highlighted in this nugget opens new opportunities for such experiments with ions like Cr3+ incorporated in different hosts e.g. Mg0, and other ions like Ti2+ in corundum. Such studies will illuminate the nature of the ground states of ions in laser materials like YAG (yitrium-aluminum-garnet) and LiNb03 Education/Broader Impact: The research reported here is the outcome of a close collaboration between the two PIs [Ramdas (Experimental) and Rodriguez (Theorist)]; X. Lu (Graduate Student); Professor S. Venugopalan (SUNY, Binghamton); Professor Hyunjung Kim (Sogang University, Korea, and Dr. Marcos Grimsditch (ANL). X. Lu and G. Chen from our group received their Ph.Ds during 2007-2008; J. Bhosale and R. Garretts are the current graduate research students. Collaborations with Professor H. Alawadhi (Univ. of Shiraz, UAE), Professor Eugene Haller (UCB), Dr. Thomas Anthony (formerly of GE) and Professor L.R. Ram-Mohan are further examples of the interactive and intellectually stimulating ambience in which our graduate students and undergraduates carry out their research; this experience prepares them for an exciting future in universities and national and industrial laboratories. Fig 2