Mass spectrometry has undergone a great deal of development as an empirical subject and many useful approaches to the analysis and identification of organic molecules have been developed without a detailed understanding of theory of ion behaviour. This is also the way in which the subject is usually approached and it is the tack adopted here. That does not mean to say that an understanding of ion behaviour is not important - it is, but that understanding is still being developed and this book is designed for those wishing to use mass spectrometry now.