Hund’s rule ground state

UO2 and Np02 are nearly insulating semiconductors crystallizing in the cubic Cap2 structure. The high-temperature magnetic susceptibilities are fully compatible with the (5f ) Hund s rule ground states for U and Np +. The presence of... 

The Hund s rule ground state of the 4f configuration of the Pr ion is H4. It is one of the few ions in which free-ion spectra are available for comparison the... 

Let us turn now to the corresponding inelastic cross-section. The matrix elements (/, M L + 2S J, M) vanish except for / —/ = 1. Hence, near the forward direction we observe only the dipole-allowed transitions, i.e., the /—> / 1 transitions out of the Hund s rule ground state. Beyond the limit of small K, higher-order transitions contribute to the cross-section, and these are the main subject of the subsequent theory valid for arbitrary values of k. The small-K result we present for inelastic events, / = / 1, is of limited practical value since the minimum value of c is usually quite large owing to the kinematic constraints on the scattering process. Even so, the result is a useful guide to the size of the cross-section, and a welcome check on a complete calculation. 

In the solid state, the interaction with the sea of conduction electrons distorts the pure atomic picture, and multiplets other than the Hund s rule ground state mix into the full wave function. In view of the success of the atomic approximation, it is likely that this mixing of different / quantum numbers is at the few percent level, nonetheless this is an assumption that should be tested. 

The Hund s rule ground state was chosen throughout ... 

In principle, all possible excitations contribute to the photoelectron spectrum and the proper quantum mechanical amplitude must be calculated. For the lanthanides, the atomic limit corresponds to the assumption that the photoelectron spectrum is dominated by those processes, where the photon hits a particular ion and causes an excitation on that ion without disturbing the remainder of the crystal. In the standard model, the lanthanide ion would initially be in its bivalent / configuration with the Hund s rule ground state multiplet (Table 1 in Section 2.2), and would be transferred into some multiplet within configuration... 

Lanthanides fluctuating between two magnetic Hund s rule ground states Pr and Tm. 

X-ray scattering studies by Darnell (1963) on the temperature dependence of the lattice constants in the lanthanides, and a truly remarkable series of experiments performed by Keating in 1969 which revealed charge scattering at twice the magnetic wave vector in Ho and ascribed it to the aspherical charge distribution of the /g Hund s rule ground state. 

Fig. 19. The measured polarization of the scattered beam from Ho at 38 K.. The solid line has been calculated by assuming that R = ( J)/(S y) = 3, as appropriate to the Hund s rule ground state of Ho. (The dashed and dotted lines have been calculated assuming that R = 4 and 2, respectively.) At small Q this provides an adecpiate description of the data, but at high Q there is a significant deviation from the expected form. Note the experiments were performed with an incident Jt geometry, so that the expressions developed in section 2 are not applicable (see Sutter et al. 1999 for details).

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