Study On The Relationship Between The Average Energy Of Valence Electrons And The ?-spectrum Of Positron Annihilation In Molecules

The interaction of low-energy positrons with atoms and molecules has been studied for many years and plays an important role in many fields.In medicine,positron emission tomography(PET)uses double gamma photon annihilation to study human metabolism.In materials,positrons are used to study material properties.In astronomy,annihilation radiation is useful for explaining astrophysical processes.The interaction between positrons and atoms and molecules has been extensively studied,but there are still many unsolved problems in the study of the annihilation mechanism.For most molecules,the existing theoretical methods and models cannot explain the obvious gap between the theoretical prediction value of positron annihilation and the experimental measurement value.The experimental measurement value is thousands of times higher than the theoretical value,especially for large molecules.In addition,how to prove quantitatively that valence electrons play a major role in positron annihilation from an experimental point of view.To solve the above problems,59 different kinds of molecules with experimental data of gamma-ray spectrum were studied.According to the conclusion that there is a linear correlation between the ram electronegativity and the positron annihilation gamma spectrum of atoms,and the definition of electronegativity proposed by Rahm(electronegativity is always based on the ground state energy of valence electrons),the average energy of valence electrons of 59 molecules is calculated,which is regarded as a scale equivalent to electronegativity.According to the discovery that the electronegativity of atoms is linearly correlated with their full width at half maximum(FWHM)and average Doppler shift(ADS),the FWHM and ADS of 59 molecules are calculated,and the average energy of valence electrons of 59 molecules are compared with them.And we get the following conclusions: There is a good linear relationship between the average energy of valence electrons and the experimental and theoretical values of the gamma ray spectrum FWHM.From the experimental point of view,the FWHM value of gamma spectrum indicates the ability of valence electrons to attract positrons.The average valence electron energy of a molecule can describe the positron annihilation spectrum.The average energy of valence electrons is taken as the reference value and compared with the experimental and theoretical values of ADS.They have a strong linear relationship.It is proved experimentally that the valence electron plays an important role in the annihilation process.There is a strong linear correlation between FWHM and ADS.In addition,ADS contains all the information of the gamma-ray spectrum.It is shown that ADS can be used as the characteristic value to describe the gamma-ray spectrum,and it is more accurate than FWHM.