Recommended reading
For an intro to LIBS use in geology see Janna Lappalainen's bachelor's thesis: Thesis pdf. , Aalto info link.
For overview on LIBS for geo applications, I recommend for example http://doi.org/10.1016/j.apgeochem.2021.104929 by Harmon and Senesi. (This is not our work)
My master's thesis on building a LIBS-Lidar Scanning laser-induced breakdown spectrometer for mine walls .
For understanding the math behind LIBS analysis and for limits of detection for all elements and other excellent material to understand LIBS see http://libs-info.com/ webpage.
To understand atomic spectra I recommend "The theory of atomic structure and spectra" Cowan, R.D. (1981) The theory of atomic structure and spectra. 7. [pr.]. Berkeley: Univ. of Calif. Press (Los Alamos series in basic and applied sciences). ISBN 978-0-520-03821-9 textbook by Cowan. It's a bit old from 1980s and heavy with 750pages but is arguably the best book on the topic and has had many reprints. For basic understanding just read the first chapter it already tells a lot.
For more reading, the listing of all references I use, you can check out my Zotero library at https://www.zotero.org/ilpo/collections/4CAJW7U9 .