Very briefly described is research conducted on the following topics: fine structure and Zeeman effect of helium; Zeeman and Stark effects of positronium; hyperfine structure of the muonic helium atom; Lamb shifts of hydrogenic ions of high Z; nonadiabatic effects in slow atomic collisions; quenching of the metastable 2S state of muonic hydrogen and the muonic helium ion; two photon absorption; and quantization of electrodynamics hyperboloids and generalization of the effective action for electrodynamics. (GRA)
The Bohr formulation—the original one—is now largely a matter of history. The usual career of a theory was its fate. It explained much, but it failed at the first signs of complication, even for the simplest molecules as hydrogen and helium. Some results were either only approximate in a loose or incomplete fashion, e.g. in the application of the correspondence principle to intensities, the only reliable predictions being only for an absence of certain lines, or they quite disagreed with experiment, e.g. in the case of the hydrogen molecule and the hydrogen molecule ion, the normal and excited states of helium, the anomalous Zeeman effect, the Ramsauer effect (the phenomenon of the deflection of electrons at low speeds being less than at higher speeds in atomic collisions), and in the treatment of problems where more than one electron was involved. In the last mentioned cases the perturbation method, so successful in solving “many-body” problems in celestial mechanics, failed completely because systems of several electrons, possessing frequencies of the order of light waves, cannot interact classically. A bit of much forced pragmatism was practiced in treating the many electron atom as a variation of the hydrogen atom. Besides, there were technical oddities, like ½ quantum numbers, and impenetrated anologies between visible and X-ray spectra.
A comprehensive set of lecture and study notes covering fundamental atomic and molecular physics. The text systematically works through the breakdown of the classical Rutherford atom and the Bohr-Sommerfeld model, followed by a full 3D Schrödinger treatment of the hydrogen atom using spherical harmonics and Laguerre polynomials. It details relativistic corrections, spin-orbit coupling, and fine structure via Clebsch-Gordan addition and Kramers' recursion relations. The notes further explore magnetic field interactions (normal and anomalous Zeeman effect, Paschen-Back effect), time-dependent perturbation theory for light-matter transitions, electric dipole selection rules, the 21-cm hyperfine splitting of hydrogen, and two-electron systems (Helium, exchange integrals, and Slater determinants). Includes extensive reference tables and angular momentum formulas.
The mean life of the 2S state of hydrogen in the absence of collisions is primarily determined by the simultaneous emission of two photons. Owing to this cause the mean life is `-*4 sec. It is expected that the mean life of is 2S `S of He i is of the same order of magnitude and is much shorter than that of is 2S 3S of He i. The non-adiabatic collisions with electrons are found to be more important than the static effects at small electron densities, leading to a transition probability `-*-`~h sec ` for an electron temper- ature `-.--`io,ooo° C and an electron density 30 cm3. The effect of static electric fields on the 2S state of hydrogen is worked out in more detail than previously by taking into account the hyperfine structure. The mean life in static electric fields which are strong enough to make double emission of little importance and yet weak enough to give a mean life > io7 sec is found to be the sum of two lives: (i) the mean life calculated neglecting hyperfine structure and (2) the mean life calculated neglecting radiation coupling. In both (i) and (2) the mixing of 2~ into 2S by the Stark effect is taken into account. Radiations due to quadrupole and magnetic dipole effects are considered qualita- tively for is 2S 3S of helium and quantitatively for 2S of hydrogen. For the latter there exists a small radiative magnetic dipole effect on Dirac's theory of the electron which is absent in the ordinary spin model
Using the quantum approach to the subject of atomic physics, this text keeps the mathematics to the minimum needed for a clear and comprehensive understanding of the material. Beginning with an introduction and treatment of atomic structure, the book goes on to deal with quantum mechanics, atomic spectra and the theory of interaction between atoms and radiation. Continuing to more complex atoms and atomic structure in general, the book concludes with a treatment of quantum optics. Appendices deal with Rutherford scattering, calculation of spin-orbit energy, derivation of the Einstein B coefficient, the Pauli Exclusion Principle and the derivation of eigenstates in helium. The book should be of interest to undergraduate physics students at intermediate and advanced level and also to those on materials science and chemistry courses.
The interaction of two excited hydrogen atoms in metastable states constitutes a theoretically interesting problem because of the quasidegenerate
2P1/2 levels that are removed from the
2S states only by the Lamb shift. The total Hamiltonian of the system is composed of the van der Waals Hamiltonian, the Lamb shift, and the hyperfine effects. The van der Waals shift becomes commensurate with the $2S\ensuremath{-}2{P}_{3/2}$ fine-structure splitting only for close approach (
R<100a0, where
a0 is the Bohr radius) and one may thus restrict the discussion to the levels with
n=2 and
J=1/2 to a good approximation. Because each
S or
P state splits into an
F=1 triplet and an
F=0 hyperfine singlet (eight states for each atom), the Hamiltonian matrix a priori is of dimension 64. A careful analysis of the symmetries of the the problem allows one to reduce the dimensionality of the most involved irreducible submatrix to 12. We determine the Hamiltonian matrices and the leading-order van der Waals shifts for states that are degenerate under the action of the unperturbed Hamiltonian (Lamb shift plus hyperfine structure). The leading first- and second-order van der Waals shifts lead to interaction energies proportional to
1/R3 and
1/R6 and are evaluated within the hyperfine manifolds. When both atoms are metastable
2S states, we find an interaction energy of order ${E}_{h}\ensuremath{\chi}{({a}_{0}/R)}^{6}$, where
Eh and
L are the Hartree and Lamb shift energies, respectively, and $\ensuremath{\chi}={E}_{h}/\mathcal{L}\ensuremath{\approx}6.22\ifmmode\times\else\texttimes\fi{}{10}^{6}$ is their ratio.