Forbidden transitions in the helium atom

Forbidden transitions in the helium atom

Nonrelativistically forbidden, single-photon transition rates between low lying states of the helium atom are rigorously derived within quantum electrodynamics theory. Equivalence of velocity and length gauges, including relativistic corrections is explicitly demonstrated. Numerical calculations of matrix elements are performed with the use of high precision variational wave functions and compa...

The effect of forbidden transitions on cosmological hydrogen and helium recombination

More than half of the atoms in the Universe recombined via forbidden transitions, so that accurate treatment of the forbidden channels is important in order to follow the cosmological recombination process with the level of precision required by future microwave anisotropy experiments. We perform a multi-level calculation of the recombination of hydrogen (H) and helium (He) with the addition of...

Radiative transitions of the helium atom in highly magnetized neutron star atmospheres

Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We present Hartree–Fock calculations of the polarization-dependent photoionization crosssections of the He atom in strong magnetic fields ranging from 1012 to 1014 G. Convenient fitting formulae for the cros...

The Structure of the Helium Atom.

Quantum-well anisotropic forbidden transitions induced by a common-atom interface potential

A prominent effect of the interface potential ~IP! @E. L. Ivchenko and A. Yu. Kaminski, Phys. Rev. B 54, 5852 ~1996!; O. Krebs and P. Voisin, Phys. Rev. Lett. 77, 1829 ~1996!#, the optical anisotropy of the forbidden transitions in quantum wells has been observed by reflectance-difference spectroscopy. Predictions by the heavy-light-hole coupling IP models are qualitatively consistent with all ...