Quantum first

Quantum chemistry and spectroscopy 

Thomas Engel 

Pearson Education | 2007 | 512pp | ?56.99 (HB) | ISBN 9780805339796 

Reviewed by Nick Green 

This book is an interesting text that tries to fulfil many objectives: to analyse in detail some simple model systems that have exact and accessible solutions; to show how spectroscopy can be understood using quantum mechanics; to show that quantum mechanics is relevant and applicable to newly developing fields.

The book starts with a fairly standard introduction to quantum mechanics through the failings of classical mechanics, the Schr?dinger equation, operators and observables and expectation values. In this part many key concepts are simply asserted and not explained, presumably to avoid mathematical overload. For example the Hermitian nature of operators and the orthogonality of wavefunctions - there is a nice vector analogy, but no hint about where this important property comes from. Students are likely to find this style of argument unsatisfactory. There is also an oversimplified discussion of quantum mechanical measurement, which deals with the idealised case where a measurement that finds an eigenvalue leaves the system in the corresponding eigenstate.

The book continues with a discussion of some exactly soluble systems: the free particle, the particle in a box, the generalisation to two and three dimensions, finite depth boxes, the harmonic oscillator and rotational motion. Again, even for the simple cases the solutions are asserted and justified a posteriori, rather than being found by solution of the Schr?dinger equation.

Then follows an introduction to vibrational and rotational spectroscopy. Here, there is just not enough and definitions are not sufficiently precise. Spectroscopy is a precise science and requires clear distinction, for example between ?0 and ?e. There is a table of molecular constants that does not specify whether they are for the vibrational ground state or are equilibrium values. Nor indeed does the book tell us how equilibrium values may be obtained (apart from dissociation energy). The confusion is made worse by a simulated infrared spectrum of HCl incorrectly centred on ?e, followed on the next page by a spectrum of CO correctly centred on ?0. Students find this distinction hard enough to grasp, and this description will not help.

In summary, parts of this book will be useful for reference, but I would not recommend it as a comprehensive text. The quantum mechanics is likely to leave students with unanswered questions and the spectroscopy does not cover enough material and in places could cause serious confusion.