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Chemical Physics Letters

On the spin-polarization in the ground state of the Cr(III) ion

Takashi Ikagawa, T. Otsuka, Youkoh Kaizu

Published Jan 1, 1996• 1 citation
Publisher
DOI
10.1016/0009-2614(95)01298-2

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Spin States and Spin Polarization

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Lecture notes in physics•Nov 1, 2011•0 citations
The spin-lattice relaxation time in the 4 A 2 ground state of C r 3 + in ruby can be on the order of magnitude of seconds at liquid helium temperatures in low magnetic fields B | | c . This allows for highly efficient optical pumping of the spin levels in this system. Such pumping can then in turn be employed to drastically increase the optical density of the inhomogeneously broadened R 1 ( ± 3 / 2 ) or R 1 ( ± 1 / 2 ) lines and also to narrow the spectral hole width because Cr–Cr electron-spin flips (cross relaxation) are suppressed in the ground state, leading to longer dephasing times T 2 ∗ . Both effects can be employed to further reduce the group velocity of light pulses propagating through a transient spectral hole.
Quantum gases of doubly polar molecules represent appealing frameworks for a variety of cross-disciplinary applications, encompassing quantum simulation and computation, controlled quantum chemistry, and precision measurements. Through a joint experimental and theoretical study, here we explore a novel class of ultracold paramagnetic polar molecules combining lithium alkali and chromium transition metal elements. Focusing on the specific bosonic isotopologue 6 Li 53 Cr , leveraging on the Fermi statistics of the parent atomic mixture and on suitable Feshbach resonances recently discovered, we produce up to 50 × 10 3 ultracold Li Cr molecules at peak phase-space densities exceeding 0.1, prepared within the least bound rotationless level of the Li Cr electronic ground state X 6 Σ + . By also developing new probing methods, we thoroughly characterize the molecular gas, demonstrating the paramagnetic nature of Li Cr dimers and the precise control of their quantum state. We investigate their stability against inelastic processes and identify a parameter region where pure Li Cr samples exhibit lifetimes exceeding 0.2 s. Parallel to this, we employ state-of-the-art quantum chemical calculations to accurately predict the properties of Li Cr ground and excited electronic states. This model, able to reproduce the experimental Li - Cr high-spin, scattering length, allows us to identify both efficient paths to coherently transfer weakly bound Li Cr dimers to their absolute ground state, and suitable transitions for their subsequent optical manipulation. Our studies establish Li - Cr as a prime candidate to realize ultracold gases of doubly polar molecules with significant electric (3.3 D) and magnetic ( 5 μ B ) dipole moments. Published by the American Physical Society 2024
Molecular quantum bits based on copper(ii) or vanadium(iv) have been shown to possess long coherence times on multiple occasions. In contrast, studies in which non-spin-½ ions are employed are relatively scarce. High-spin ions provide additional states that can be used to encode further quantum bits. Furthermore, an optical rather than a microwave readout of molecular quantum bits is highly desirable, because in principle it could allow addressing at the single quantum bit level. The chromium(iii) complex [Cr(ddpd)2]3+ (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) combines both the large spin (S = 3/2) and optical activity (strong, long lived luminescence). Here we demonstrate that the compound possesses coherence times of up to 8.4(1) μs, which are much longer (at least three times) than those for other chromium(iii)-based compounds. On the other hand, it is proved to be impossible to read out or influence the quantum state by optical means, underlining that further work is needed in this direction.