Ionization energies of organic compounds are very important for studies of electronic structures, ionized states and molecular reaction mechanics. Ionization energies can ordinary be obtained by HeI photoelectron spectra. Our project is development of photoelectron spectrometer that is suitable for a very small amount of samples and heating more than 300ﾟC.
As a result, our aim was attained as followings. Photoelectron spectra of DNA bases such as cytosine, thiocytosine, uracil and thiouracil were measured at heating about 300ﾟC and with a smaller amount of sample than 100mg. The keto-enol conformation of these molecules was discussed in relation to assignment of their photoelectron spectra.
In addition, measurements of photoelectron spectra were carried out for 1,2,4-butanetriol derivatives, spiro [2、4] compounds (-heptadiene, -heptene, and-heptane substituted with methyl or cyclopropyl) and alkanes (CnH2n+1 ; n=6-14). Their spectra were assigned by comparison with molecular orbital energies obtained with the semi-empirical molecular calculations of MNDO-PM3 and AM1 methods.