Scientists / Open questions

John H. Van Vleck

Quantum mechanics; magnetism

1977 Nobel Prize in Physics

19 questions

Determination of the rank-4 and rank-6 anisotropic Eu3+–Fe3+ exchange parameters and the origin of the anomalously large zero-field-splitting shift of Fe3+ in europium gallium garnet
Exchange narrowing of internal-electric-field (crystalline Stark) broadening in paramagnetic salts: a quantitative line-shape theory for the exchange-dominated regime
Physical origin of the reported azimuthal variation of the Verdet constant within the basal plane of tysonite at low temperatures
Persistence and magnitude of microscopic structure-dependent corrections to the dielectric constant of dilute solutions of polar molecules in non-polar solvents
The samarium crossover: quantitative crystal-field, exchange, and J-mixing theory of the Sm3+ ion in SmAl2 and samarium iron garnet (White and Van Vleck, 1961)
The origin of the water-vapor continuum: Van Vleck's residual microwave and millimeter absorption by uncondensed water vapor
Microscopic origin, sign, and magnitude of the small exchange interaction in the antiferromagnetic ordering of the chrome alums
First-principles prediction of the density correction to the Clausius–Mossotti function of strongly polar gases: the unresolved ammonia λ discrepancy from Van Vleck's translational fluctuation calculation
Critical conditions for ferromagnetism in the localized-electron theory with nonorthogonality: a controlled microscopic determination
The detailed line shape of dipolar-broadened magnetic resonance lines in crystals beyond the Van Vleck moment expansion
Testing and refining the crystalline-field model for the magnetic susceptibility of nitric oxide adsorbed on silica gel: low-temperature behavior, hindered rotation, and site heterogeneity
Microscopic quantitative theory of non-cubic ligand-field coefficients and Jahn–Teller–spin–orbit coupling in specific cation–ligand complexes (van Vleck, 1958)
Microscopic mechanism of the ferromagnetic-resonance linewidth and relaxation in europium iron garnet (Eu $_3$ Fe $_5$ O $_{12}$ )
Microscopic mechanism of the ferromagnetic exchange coupling in insulating EuO
Quantitative microscopic theory of the temperature-dependent cubic magnetocrystalline anisotropy constants $K_1$ and $K_2$ of iron and nickel
Origin of the ~88 K (about 61 cm $^{-1}$ ) absorption of Tm $^{3+}$ in thulium iron garnet and a quantitative microscopic account of its low-energy levels and exchange couplings
Dirac-electron hidden momentum beyond order $1/c^2$ : higher-order spin corrections and force balance under nonzero average acceleration
Precision $g_J$ factors of the $2s^22p^4\,{}^3P$ ground term of atomic oxygen: the residual discrepancies, the common-mode wave-function error, and the off-diagonal spin–orbit element $\langle{}^3P_2|\zeta_{2p}|{}^1D_2\rangle$
Consistent microscopic theory of europium iron garnet: the factor-of-two Eu quadrupolar-splitting discrepancy and the undetermined fourth-degree anisotropic-exchange coefficients

Back to open problems

Determination of the rank-4 and rank-6 anisotropic Eu3+–Fe3+ exchange parameters and the origin of the anomalously large zero-field-splitting shift of Fe3+ in europium gallium garnet

Exchange narrowing of internal-electric-field (crystalline Stark) broadening in paramagnetic salts: a quantitative line-shape theory for the exchange-dominated regime

Physical origin of the reported azimuthal variation of the Verdet constant within the basal plane of tysonite at low temperatures

Persistence and magnitude of microscopic structure-dependent corrections to the dielectric constant of dilute solutions of polar molecules in non-polar solvents

The samarium crossover: quantitative crystal-field, exchange, and J-mixing theory of the Sm3+ ion in SmAl2 and samarium iron garnet (White and Van Vleck, 1961)

The origin of the water-vapor continuum: Van Vleck's residual microwave and millimeter absorption by uncondensed water vapor

Microscopic origin, sign, and magnitude of the small exchange interaction in the antiferromagnetic ordering of the chrome alums

First-principles prediction of the density correction to the Clausius–Mossotti function of strongly polar gases: the unresolved ammonia λ discrepancy from Van Vleck's translational fluctuation calculation

Critical conditions for ferromagnetism in the localized-electron theory with nonorthogonality: a controlled microscopic determination

The detailed line shape of dipolar-broadened magnetic resonance lines in crystals beyond the Van Vleck moment expansion

Testing and refining the crystalline-field model for the magnetic susceptibility of nitric oxide adsorbed on silica gel: low-temperature behavior, hindered rotation, and site heterogeneity

Microscopic quantitative theory of non-cubic ligand-field coefficients and Jahn–Teller–spin–orbit coupling in specific cation–ligand complexes (van Vleck, 1958)

Microscopic mechanism of the ferromagnetic-resonance linewidth and relaxation in europium iron garnet (Eu3_33​Fe5_55​O12_{12}12​)

Microscopic mechanism of the ferromagnetic exchange coupling in insulating EuO

Quantitative microscopic theory of the temperature-dependent cubic magnetocrystalline anisotropy constants K1K_1K1​ and K2K_2K2​ of iron and nickel

Origin of the ~88 K (about 61 cm−1^{-1}−1) absorption of Tm3+^{3+}3+ in thulium iron garnet and a quantitative microscopic account of its low-energy levels and exchange couplings

Dirac-electron hidden momentum beyond order 1/c21/c^21/c2: higher-order spin corrections and force balance under nonzero average acceleration

Precision gJg_JgJ​ factors of the 2s22p4 3P2s^22p^4\,{}^3P2s22p43P ground term of atomic oxygen: the residual discrepancies, the common-mode wave-function error, and the off-diagonal spin–orbit element ⟨3P2∣ζ2p∣1D2⟩\langle{}^3P_2|\zeta_{2p}|{}^1D_2\rangle⟨3P2​∣ζ2p​∣1D2​⟩

Consistent microscopic theory of europium iron garnet: the factor-of-two Eu quadrupolar-splitting discrepancy and the undetermined fourth-degree anisotropic-exchange coefficients

Microscopic mechanism of the ferromagnetic-resonance linewidth and relaxation in europium iron garnet (Eu $_3$ Fe $_5$ O $_{12}$ )

Quantitative microscopic theory of the temperature-dependent cubic magnetocrystalline anisotropy constants $K_1$ and $K_2$ of iron and nickel

Origin of the ~88 K (about 61 cm $^{-1}$ ) absorption of Tm $^{3+}$ in thulium iron garnet and a quantitative microscopic account of its low-energy levels and exchange couplings

Dirac-electron hidden momentum beyond order $1/c^2$ : higher-order spin corrections and force balance under nonzero average acceleration

Precision $g_J$ factors of the $2s^22p^4\,{}^3P$ ground term of atomic oxygen: the residual discrepancies, the common-mode wave-function error, and the off-diagonal spin–orbit element $\langle{}^3P_2|\zeta_{2p}|{}^1D_2\rangle$