Emission spectra of phenol, anisole, and phenetole by controlled electron impact

Upon the impact of an electron beam (100-450 eV) on PhOH, PhOCH3, PhOC2H5, PhCOCH3, and (Ph)2-CO at low pressures, the S1 emission of the parent molecule (not from PhCOCH3 and (Ph)2CO) and the photoemissions from such fragments as H, CH, CO, CO+, and OH were observed in the 200-520 nm region. It was concluded that the S1 emission of the parent molecule originates through both the S0→S1 and S0→S2 (cascade) → S1 excitation processes and that the direct excitation into the lower vibronic levels of S1 is responsible for the appearance of the vibrational structures. Most excited species including Co+(A) from PhOH were confirmed to be primarily produced; however, CO+(A) from PhOCH3, PhOC2H5, and PhCOCH3, and CO(b) from PhCOCH3 were found to be produced competitively through one-electron and two-electron excitation processes in relation to the intensity measurements. The relative contribution of the two-electron excitation process in producing CO+(A) increased with a larger substituent, and it was larger than that for CO(b) in PhCOCH3. (auth.)