Interacting Rydberg and valence states in radicals and molecules: experimental and theoretical studies

This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. This review discusses low-lying (n ¼ 3) Rydberg electronic states of molecules and radicals, in particular those that result in mixed configurations and participate in non-adiabatic interactions. Rydberg-valence interactions are ubiquitous in molecules and radicals and have important effects on potential energy surface shapes, spectroscopy, and dissociation dynamics. The review emphasises selected properties that are affected by these interactions and illustrates them with several examples, mostly involving free radicals, in which collaboration between experimental and theoretical investigations has been crucial for understanding. Specifically, the cases of substituted methyl, vinyl, and hydroxyalkyl radicals are described, as well as Rydberg states of diazomethane and the ethyl radical. The issue of triple conical intersections is also briefly discussed.