Book Review  

Energy Levels in Atoms and Molecules
by W. G. Richards and P. R. Scott

 Reviewed by
Upali A. Jayasooriya
School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, Norfolk, England.
u.jayasooriya@uea.ac.uk
 

Energy Levels in Atoms and Molecules, by W. G. Richards and P. R. Scott. Oxford University Press: Oxford, UK, 1994; 96 pp, 246 mm × 189 mm, softcover ISBN 0-19-855804-X, £ 6.99.

I enjoyed reading this well-written and easy-to-read book, one of the Oxford Primer Series. It is constructed somewhat like a collection of lecture notes; all topics are treated at a level appropriate to senior undergraduates or postgraduate students.

Energy levels in atoms are treated first, starting with the photoelectric effect, wave–particle duality, units and measurements, and the electromagnetic spectrum. Energy levels of the hydrogen atom are used to introduce wave mechanics, quantum numbers, hydrogen wave functions, electron spin, Pauli principle, the periodic table, Hund's rule, and ionization energies. The energy levels of atoms are discussed with coupling of angular momenta, Russell–Saunders coupling, term symbols, and closed electron shells. This is followed by a discussion of some simple atoms, helium as a model for photochemistry, spin–orbit coupling, and jj coupling.

The second chapter concentrates on diatomic molecules. It deals with the orbital and LCAO approximations, bonding and antibonding molecular orbitals, molecular orbital diagrams, molecular electronic energy levels, vibrational energy levels, rotational energy levels including the effects of nuclear spin, excitation energies, and populations.

The third chapter extends the discussion to polyatomic molecules. It deals with orbitals in polyatomic molecules, water, molecular shape, sp³ and other hybridizations, delocalization in benzene, excited states in organic compounds, Walsh diagrams, transition metal complexes in their ground and excited states, Rydberg states, photoelectron spectroscopy, vibrational energy levels and characteristic frequencies, rotational energy levels, and inversion in ammonia.

Energy levels in NMR are discussed in the final chapter, which includes the effect of magnetic fields on atomic energy levels, basic principles of NMR, chemical shifts, spin-spin coupling, rate processes, double resonance, NMR of solids, relaxation times, basic principles of ESR, hyperfine structure, and the g value.

This final chapter on NMR seems somewhat out of place compared to the remaining subject matter. Perhaps it would be more appropriate to include a chapter on "Energy Levels Between Spin States," with a general description of spin resonance methods such as NMR, ESR, Mossbauer, MuSR, etc. Only magnetic field effects are discussed; an additional discussion of electric field effects would have made this section more complete. Another significant omission is the energy levels due to magnetic exchange between metal atoms. My enjoyment of the book was marred by several typographical errors. Those that seem to affect the logic of the discussion are given below.

Appendix—typographical errors

Page 22, 6th line: The term symbols should be ²P_3/2 and ²P_1/2 and not ²S_3/2 and ²S_1/2.
Page 31, 7th line: The equation should be p = 1s_A - 1s_B
Page 49: Figure 3.3 depicting the sp² hybridization in ethene should be modified to show the correct geometry.
Page 55: The end of second paragraph says, thus for BH₂: It should be for BH₂⁺.
Page 57, 5th paragraph: It is wrong to use the symbols t_2g and eg for tetrahedral geometry. These should be simply t₂ and e.
Page 62: Table 3.3 gives no indication as to which vibration is being refered to. For example C=C-H has a frequency of 2260–2100 cm^-1. This molecular unit has three vibrations; the authors should be more specific. C-O at 1780–1660 cm^-1 is incorrect.