FINE STRUCTURE IN DOUBLET--QUARTER ANTICROSSINGS IN CN

Author Institution: Bell LaboratoriesRecently, anticrossings have been observed between 11 pairs of rotational levels of the $B ^{2}\Sigma^{+}$ and $a ^{4}\Sigma^{+}$ states of the CN radical. The position of the anticrossings allow a determination of the rotational constant, centrifugal sidtortion, and the separation of the N = 0 lavels. The anticrossing spectra also show effects of the fine structure of these states (spin-rotation coupling in th $^{2}\Sigma^{+}$ state and spin-rotation and spin-spin coupling in the $^{4}\Sigma^{+} state).$ Experiments upon and analyses of these effects are in progress and will be reported upo

GAS PHASE EPR LINEWIDTHS AND INTERMOLECULAR POTENTIALS

Author Institution: Bell LaboratoriesMeasurements on line broadening collision cross-sections have been carried out using gas phase EPR techniques, A number of simple systems involving halogen atoms and molecules and inert gases have been investigated. The measured cross-sections show a dependence on the magnetic quantum number, thus indicating an anisotropy in the intermolecular potential. Very large differences in cross-sections for different fine structure states are also observed. Detailed comparisons between the experimental results and theoretical predictions are possible

DOUBLET-QUARTET ANTICROSSINGS

Author Institution: Bell LaboratoriesA number of small diatomic radicals have bound doublet and quartet states. Examples of such systems include $CN, N_{2}{^{+}}, C_{2}{^{-}}$, and $O_{2}{^{+}}$. Since optical selection rules forbid the intercombination of the quartet and doublet states, the excitation energy to the lowest quartet and its structure is usually poorly known. Previously, we have reported doublet-quartet anticrossings in CN, and we now present a description of the fine structure of the $B^{2}\Sigma^{+}$ and $a^{4}\Sigma^{+}$ states of CN based upon an analysis of these anticrossings. We also report newly observed doublet-quartet anticrossings in $O_{2}{^{+}}$

Thermodynamic and Electron Diffraction Signatures of Charge and Spin Ordering in La1-xCaxMnO3

The large-magnetoresistance compounds La1-xCaxMnO3 have been studied using specific heat, sound velocity (v), and electron diffraction. For 0.63 ≤ x ≤ 0.67 charge ordering is observed at 260 K and accompanied by a dramatic (>10%) increase in v. This simultaneous occurrence of electron and lattice ordering features implies extremely strong electron-phonon coupling, known to exist for the octahederally coordinated d4 ion and originating in the Jahn-Teller effect. A dynamic manifestation of this Jahn-Teller coupling has been suggested by Millis et al. as the origin for colossal magnetoresistance.