Paul B. Dorain

Optical Spectra of Os4+ in Single Cubic Crystals at 4.2°K

The optical spectra of Os4+ (5d4) in single cubic crystals of K2PtCl6, Cs2ZrCl6, Cs2HfCl6, and Rb2ZrCl6 at 4.2°K has been studied. The spectrum is characterized by very narrow lines in the region from 10 000–36 000 cm−1. Vibrational structure is observed which may be assigned to the ungerade modes of the OsCl62− complex in the lattice. A crystal‐field analysis within the d4 manifold fits the observed ten electronic, 0–0 transitions with an rms deviation of 228 cm−1 for the parameters A = 0, B = 741, C = 1296, V = 22490, and λ5d = 2416 cm−1. The calculated molar magnetic susceptibility agrees with that found for concentrated crystals such as K2OsCl6 and Cs2OsCl6. The analysis of the electronic states was dependent upon a calculation of intensities for the t2g4 → t2g3eg transitions. The calculated results are given for a tetragonal distortion of the cubic field and are shown to qualitatively agree with the linewidth of the transitions. The calculated g values for all observed transitions are tabulated. Fina...

Spin Resonance of SnO2:V and the Vanadium 3d Electron Orbital

The ESR spectrum of SnO2 containing about 0.5% vanadium observed in K band at liquid‐nitrogen temperature shows two sets of shfs. Relative intensity measurements show that the large shfs (168 G) is due to the two tins located along the c axis and the small shfs (28 G) due to the four tins lying in a diagonal plane of the unit cell containing four oxygens. The large shfs is largely isotropic, with an axial maximum along the c axis. This suggests that the ground electron level is 3d(x2−y2). The next level is 3d(xz). This is deduced from the g values (gxx=1.939,gyy=1.903,and gzz=1.943).

Electron Paramagnetic Resonance of Sulfur Monoxide

Four electron paramagnetic resonance transitions of the SO free radical generated in a gas‐phase discharge of SO2 have been observed and assigned. The lines result from electric‐dipole transitions between the Zeeman levels of the K = 1, J = 1 → K = 2, J = 1 states of the 3Σ− electronic ground state of 32S16O and 34S16O. The rotational constant B0 and the splitting constants λ and μ have been obtained from the microwave investigation of Powell and Lide. The g values of the electron spin, the orbital, and the rotational magnetic moments of 32S16O as determined from least‐squares fitting of the EPR data are gs = 2.00197, gl = 0.00371, and gr = 0.00019. The frequencies of the corresponding transitions for the less abundant species, 34S16O, have been calculated from the isotope corrected 32S16O parameters. The relative intensities and linewidths of the SO spectrum are discussed. The linewidth is attributed to the collision broadening of SO by SO2.

Optical Spectrum of Re4+ in Single Crystals of K2PtCl6 and Cs2ZrCl6 at 4.2°K

The optical spectrum of Re4+(5d3) has been studied at 4.2°K in single crystals of K2PtCl6 and Cs2ZrCl6. The spectrum is characterized by extremely narrow lines in the region from 8500 to 36 000 cm−1. Vibrational structure is observed which is assigned to the odd modes of the ReCl62− complex. A crystal‐field analysis of the 0–0 transitions fits the observed eight electronic transitions with an rms deviation of 209 cm−1 for the parameters A = 0, B = 327 cm−1, C = 1818 cm−1, V = 30 347 cm−1, and λ5d=2392 cm−1. Magnetic‐field measurements of the excited states give g values which are compared with theory. A discussion of the intensities of the transitions is presented which demonstrates that some absorptions observed are magnetic‐dipole transitions. Finally, several conclusions about the study of optical spectra of dn systems are presented.

An analysis of the optical spectra of single crystals of Cs2NaPrCl6

The optical spectra of single crystals of Cs2NaPrCl6 are reported. A complete f2 analysis gives the parameters: F2=302.0 cm−1, F4/F2=0.1600, F6/F2=0.01596, ξ4f=754.8 cm−1, α=19. cm−1, A4〈r4〉=288.6 cm−1 and A6〈r6〉=39.6 cm−1. A comparison of these parameters with those of the free Pr+3 ion indicates a covalency of 3%. The magnetic susceptibility is calculated and compared to that measured previously.

Electron Paramagnetic Resonance of Re4+ in Single Crystals of K2PtCl6

The electron paramagnetic resonance of Re4+ in single cubic crystals of K2PtCl6 at wavelengths of 3 cm, 1 cm, and 8 mm is reported. The experimental results were analyzed assuming the Re4+ ground state is a spin quartet with S=32 and I=52. The cubic spin Hamiltonian is given by H=gβH·S+AI·S+uβ{HxSx3+HySy3+HzSz3−15(H·S)(3S2−1)} +U{IxSx3+IySy3+IzSz3−15(I·S)(3S2−1)}. The third‐order terms in S in the spin Hamiltonian were found to make a significant contribution as shown by the strong angular dependence of the resonance spectrum even in a cubic field. The main transitions were between the MS=±½ Zeeman levels. In addition to the ΔmI=0 transitions, the forbidden ΔmI=±1 transitions were observed with the transition probability of the latter showing strong field dependence. Analysis of the data gave the following values for the parameters: g=1.815±0.001,u=(−13±1)×10−3,A=(3.89±0.01)×10−2cm−1,U=(−3.8±0.1)×10−3cm−1. A brief discussion of the experimental parameters is given.

Vibronic splitting of Γ8 electronic states of Ir+4 in single crystals of Cs2ZrCl6 at 4.2 °K

Single cubic crystals of Cs2ZrCl6 containing Ir+4 exhibit two absorption bands with extensive vibronic structure at 4.2 °K. Two progressions in the symmetric stretch mode (ν1) show a splitting of the absorption lines as a function of the number of quanta of the ν1 mode. Analysis shows that the electronic transitions must be from the ground Γ7(2T2g, t2g5) state to excited Γ8 quartet states, which are coupled to a threefold degenerate vibration mode of symmetry Γ4 or Γ5 and n modes of the ν1 mode. Zeeman measurements at 70 kG confirm the assignment for one progression. Arguments are presented to show that the threefold degenerate vibration mode corresponds to the transverse components of the ν4(Γ4u) mode of the face‐centered cubic lattice.

Intensities in Octahedral Complexes of 4d and 5d Transition‐Metal Ions

The theory of the intensity of vibronically allowed electric dipole transitions for octahedral complexes is investigated. The calculation is carried out within the confines of ligand field theory and full account is taken of spin–orbit coupling. Of particular interest are those transitions which take place with a considerable change of internuclear configuration and which may be characterized as mainly involving a t2gn → t2gn−1eg transition. Certain selection rules are determined and an approximate two‐parameter form is found for the intensity of the allowed transitions. This calculation is particularly useful as an aid in assigning transitions in regions where there are many possible states. Application is made to the low‐temperature optical spectra of Os4+ and of Re4+ in single crystals of Cs2ZrCl6. The spectra of OsF6 are also discussed. Some predictions are made about the low‐temperature optical spectra of W4+, Ir4+, and Pt4+ in single crystals of Cs2ZrCl6.

Zeeman polarization measurements and the vibronic coupling of Re4+ in single crystals of K2PtCl6

Zeeman polarization measurements at 70 kG and 2°K of the t2g3, 4A2g, Γ8 to t2g3, 2T2g, Γ7 electronic and vibronic transitions of Re4+ in single crystals of K2PtCl6 have been performed. The right and left circular polarized spectra of the 0–0 transition are readily explained. It is shown that describing the vibronic excited states as arising solely from the coupling of the excited electronic state to the k = 0 vibrational modes of K2ReCl6 predicts incorrect selection rules. To describe the number of lines and observed polarization properties in the vibronic spectrum, it is necessary to consider the vibronic excited states as arising from the coupling of the impurity ion electronic state to the vibrations of the whole lattice and not simply to the k = 0 vibrations.

Angular Modulation of the Magnetic Field in Electron Paramagnetic Resonance Experiments

An analysis of the use of angular modulation of the dc magnetic field used in electron paramagnetic resonance is presented. The equations which are derived show that angularly dependent paramagnetic resonance lines may be separated from angularly independent lines. Experiments with Cr2+ in CdS show agreement with the theory.