Diatomic molecules are molecules with two atoms in their structure. This could be two atoms attached to one nucleus or two atoms attached to more than one nucleus (heteronuclear). The two most important attributes of a spectral line are its position in the electromagnetic spectrum and the strength with which the molecule can interact with the radiation field to produce spectral lines. Thus, this book shows the calculation of positions and intensities of spectral lines produced by a diatomic molecule, showing the application of quantum theory to the diatomic molecule.

In this book, the authors describe how quantum mechanics can be used to predict diatomic molecule spectra in a gaseous state by discussing the calculation of their spectral line intensities. The book provides a comprehensive overview on diatomic molecule fundamentals before emphasising the applications of spectroscopy predictions in analysis of experimental data. With over 30 years of experience in measurements and quantitative analysis of recorded data, the authors communicate valuable references to any academic engaged in the field of spectroscopy and the book serves as a comprehensive guide to anyone with a genuine interest in the subject. This new edition includes three new chapters including Abel Inversion of recorded data, measurement of shadowgraphs, and application of line strength data for analysis of light from excited 2-atom molecules.

Christian Parigger has been an Associate Professor of Physics and Astronomy at the University of Tennessee from 1996 to 2023. His research interests include fundamental and applied spectroscopy, nonlinear optics, quantum optics, ultrafast phenomena, ultrasensitive diagnostics, lasers, combustion and plasma physics, optical diagnostics, biomedical applications, and in general, atomic and molecular and optical (AMO) Physics. His work encompasses experimental, theoretical and computational research together with teaching, service, and outreach at the Center for Laser Applications (CLA) at The University of Tennessee Space Institute, USA.

James Hornkohl has made research contributions encompassing spectroscopy of diatomic molecules and its application to diagnosis of combustion, plasmas, rocket propulsion and related problems. The extensive collaboration of the two authors during more than 30 years at the CLA has been most stimulating and encouraging.

Preface

Acknowledgements

Author biographies

Part I: Fundamentals of the diatomic molecule

1 Primer on diatomic spectroscopy

2 Formal quantum mechanics of diatomic molecular spectroscopy

3 Line strength computations

4 Framework of the Wigner-Witmer eigenfunction

5 Derivation of the Wigner-Witnmer eigenfunction

6 Diatomic formula inferred from the Wigner-Witmer eigenfunction

7 Hund's cases (a) and (b)

8 Basis set for the diatomic molecule

9 Angular momentum states of diatomic molecules

10 Diatomic parity

11 The condon and Shortley line strength

12 Hönl-London line-strength factors in Hund's Cases (a) and (b)

13 Using the Morse potential in diatomic spectroscopy

Part II

14 Introduction to applications of diatomic spectroscopy

15 Computation of selected diatomic spectra

16 Experimental arrangement for laser-plasma diagnosis

17 Methylidyne, CH, cavity ring-down spectrsocopy in a microwave plasma discharge

18 Cyanide, CN

19 Cyanide molecular laser-induced breakdown spectroscopy with current databases

20 Diatomic carbon, C2

21 Laser plasma carbon Swan bands fitting with current databases

22 Aluminium monoxide, A1O

23 A10 laser-plasma emission spectra analysis with current databases

24 Hydroxyl, OH

25 Hydroxyl laser-plasma emission spectra analysis with current databases

26 OH laser-induced breakdown spectroscopy and shadowgraphy

27 Titanium Monoxide, TiO

28 Nitric Oxide, NO

29 Radial electron density measurements in laser plasma from Abel-inverted hydrogen Balmer beta line profiles

30 Hypersonic imaging and emission spectroscopy of hydrogen and cyanide following laser-induced optical breakdown

Part III

Appendix A: Review of angular momentum commutators

Appendix B: Effects of raising and lowering operators

Appendix C: Modified Boltzmann plots

Appendix D: Aspects of nitric oxide computations

Appendix E: Parity in diamotic molecules

Appendix F: Rotational line strengths for the CN BX (5,4) band

Appendix G: Intrinsic parity of diatomic molecule

Appendix H: Review of diatomic laser-induced breakdown spectroscopy

Appendix I: Program MorseFCF.for

Appendix J: Boltzmann equilibrium spectrum (BESP) and Nelder-Mead temperature (NMT) scripts

Appendix K: Abel-inversion scripts

Appendix L: LIBS: 2018 to 2023 publications that include C.G.P