Rydberg state, of ethylene

Figure 2.15 Computed potential energy curves of low-energy states of (a) and ethylene (b), as a function of intemuclear separation R and of twist angle 0, respectively. Rydberg states of ethylene are indicated by letter R. (Source Wen 2015 (27). Reproduced with permission of American Chemical Society.)...

The Rydberg state of alkene is designated as n, R(3s), to specify that one electron from the n bond remains in the n orbital and the other has been shifted to the Rydberg orbital, which resembles the 3s orbital of a helium atom. The Rydberg state of an alkene is considered to have a partially ionic stmcmre such that a net positive charge remains on a carbon atom. The Rydberg state of ethylene is shown below. 

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