Excitation Number: Characterizing Multiply Excited States

Giuseppe M.J. Barca, Andrew T.B. Gilbert, Peter M.W. Gill*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    46 Citations (Scopus)


    How many electrons are excited in an electronic transition? In this Letter, we introduce the excitation number η to answer this question when the initial and final states are each modeled by a single-determinant wave function. We show that calculated η values lie close to positive integers, leading to unambiguous assignments of the number of excited electrons. This contrasts with previous definitions of excitation quantities which can lead to mis-assignments. We consider several examples where η provides improved excited-state characterizations.

    Original languageEnglish
    Pages (from-to)9-13
    Number of pages5
    JournalJournal of Chemical Theory and Computation
    Issue number1
    Publication statusPublished - 9 Jan 2018


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