Order Spin Orbit Research Articles

Magnetic circular dichroism spectrum of the tetraiodonickelate(II) ion

Magnetic circular dichroism (MCD) measurements are reported from 4.2 to 37 K and 7 to 46 kG on crystals of (N(C2H5)4)2 ZnI4 doped with NiI2–4. The charge transfer absorption and the ligand-field bands arising from transitions from 3T1(3F) to components of 1G were examined. From the temperature dependence of the MCD it is concluded that the first order spin-orbit splitting of the 3T1 ground state is almost completely quenched; the components span no more than about 20 cm–1, compared with several hundred cm–1 predicted by simple crystal field theory. The small separations between the excited components of the ground state necessitate consideration of temperature dependent B-term contributions to the MCD. Assignments of the ligand-field transitions are confirmed by linear polarisation measurements. Two possible reasons for the quenching of the ground state multiplet are discussed.

Effect of the second order spin orbit and spin-spin interactions on the 4E (G) level of Mn 2+ in ZnS

An interpretation of the structure of the 6 A 1 → { 1 A 1, 4 E} zero phonon and phonon assisted transitions is given. Covalency effects show that the 6 A 1 → 4 A 1 and 6 A 1 → 4 E transitions are well separated; consequently none of the experimentally observed lines can be due to the 6 A 1 → 4 A 1 transition. The fine structure for the 4 E level is interpreted in terms of the spin-spin and spin-orbit interactions. The results obtained are consistent with experiments.

High vibrational level predissociation in the A2Σ+state of OD

Using high resolution spectrograms, the broadened linewidths for several bands of the B2Sigma+-A2Sigma+system of OD have been reinvestigated. Comparison between observed and calculated halfwidths shows that the high-vibrational level predissociation is a case c+one, due to a first order spin orbit interaction, with a repulsive4Pi state which crosses the A2Sigma+state of OD at r=1.65 AA between v=7 and v=8, and between v=5 and v=6 for OH. The vibration- rotation interaction is shown to be responsible for the strong halfwidth dependence on the rotational quantum number.

The Theory of the Magnetic Quenching of Iodine Fluorescence and ofΛ-Doubling inΠ03States

A theoretical basis is given for Turner's proposal that the magnetic quenching of iodine fluorescence is a predissociation phenomenon. To this end it is shown that a magnetic field introduces matrix elements in the Hamiltonian function between the ${^{3}\ensuremath{\Pi}_{0}}^{+}$ and ${^{3}\ensuremath{\Pi}_{0}}^{\ensuremath{-}}$ (or possibly the ${^{3}\ensuremath{\Pi}_{0}}^{+}$ and ${^{3}\ensuremath{\Sigma}_{0}}^{+}$) states, respectively stable and unstable in ${\mathrm{I}}_{2}$. This confirms Mulliken's assignment of ${^{3}\ensuremath{\Pi}_{0}}^{+}$ to the upper state of the halogen visible bands. The magnetic field has a unique role for so-called ${0}^{+}$, ${0}^{\ensuremath{-}}$ levels because perturbations between these particular states cannot arise from rotational distortion, the cause of the usual Kronig predissociation, or from electric fields unless they are very large or else markedly inhomogeneous. The magnetic quenching should be independent of the rotational quantum number (section 5) and should depend on field strength in the form $\frac{b{\mathfrak{H}}^{2}}{(a+b{\mathfrak{H}}^{2})}$. The observed mode of frequency dependence demands that in ${\mathrm{I}}_{2}$ the potential curves of ${^{3}\ensuremath{\Pi}_{0}}^{+}$, ${^{3}\ensuremath{\Pi}_{0}}^{\ensuremath{-}}$ states, which are the two components of a $\ensuremath{\Lambda}$-doublet, be extremely close for certain values of $r$ or else actually cross each other. This crossing is shown to be theoretically possible under certain conditions. The possibility of magnetic predissociation in other molecules is also discussed. The predissociation due to collision observed by Turner, Kaplan, and others probably arises because electric fields can blend $u$ and $g$ states, and also ${0}^{+}$ and ${0}^{\ensuremath{-}}$ states if inhomogeneous.Incidental points in halogen band spectra are discussed. Schlapp's intensity theory confirms Brown's assignment of $^{3}\ensuremath{\Pi}_{1}$ to his new level in ${\mathrm{I}}_{2}$, ${\mathrm{Br}}_{2}$. A calculation is given showing why the ${^{3}\ensuremath{\Pi}_{0}}^{+}$ level in ICl appears derived from $^{2}P_{\frac{3}{2}}(\mathrm{I})+^{2}P_{\frac{1}{2}}(\mathrm{Cl})$ when configuration theory (the non-crossing rule) suggests $^{2}P_{\frac{3}{2}}+^{2}P_{\frac{3}{2}}$. An explicit mechanism is thus furnished for Brown and Gibson's interpretation of the predissociation of ICl published elsewhere in this issue.The writer's previous formulas for the width of $\ensuremath{\Lambda}$-doublets in $^{3}\ensuremath{\Pi}_{0}$ states are extended to include investigation of the sign of the doublet and the perturbations from $^{1}\ensuremath{\Sigma}$, $^{5}\ensuremath{\Sigma}$ states previously omitted although coordinate in importance with those from $^{3}\ensuremath{\Sigma}$. The need of considering these inter-system interactions is caused by the fact that the doubling is a second rather than first order spin-orbit effect. The structural form of the secular determinants inclusive of spin-orbit terms is exhibited for molecules arising from $^{2}P+^{2}P$, $^{2}P+^{2}P^{\ensuremath{'}}$, and $^{2}P+^{2}S$.