On the valence shell electronic spectroscopy of 2-vinyl furan

The vacuum ultraviolet (VUV) absorption spectrum (3.50–10.33 eV, 350–120 nm) of gaseous 2-vinyl furan has been measured for the first time using both synchrotron radiation source and electron energy loss spectroscopies with absolute cross section determinations. The He I photoelectron spectrum obtained at higher resolution than previously has been interpreted with the aid of semiempirical molecular orbital calculations. Three excited states of type $ππ*1$ are found responsible for an intense and structured first band observed between 4.2 and 5.8 eV (295–214 nm). Three triplet states were detected for the first time at about 2.46, 3.35, and 3.8 eV (477, 370, and 328 nm) which are, from the calculations, assigned as $ππ*3.$ Some partial Rydberg series, linked to $IE1$ and $IE2$ are identified. The VUV absorption spectrum bears little resemblance to that of the parent compound, furan. The electronically excited molecule is found akin to a linear polyene.