Relation between Electron Scattering Resonances of Isolated NTCDA Molecules and Maxima in the Density of Unoccupied States of Condensed NTCDA Layers

Abstract

The empty-level structure of the 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) molecule is characterized by means of dissociative electron attachment (DEA) experiments in the gas phase coupled with DFT calculations. Distinct maxima in the anion currents generated by electron attachment to NTCDA, as a function of incident electron energy, are ascribed to capture of incident electrons into empty orbitals, i.e., the process referred to as shape resonance. The empty orbital energies of gas-phase NTCDA shifted to 1.2 eV lower energy reproduce satisfactorily the maxima of the unoccupied electronic states of a multilayer NTCDA film measured by means of the very low energy electron diffraction method and the total current spectroscopy measurement scheme. The present results indicate that the empty levels of individual NTCDA molecules are stabilized in the solid state, but their relative energies remain nearly unaltered. The stabilization energy in multilayer film of NTCDA molecules is likely due to attractive polarization forces. Fragmentation of the gas-phase NTCDA temporary parent anions via the DEA mechanism, the other issue of the present investigation, leads to the rupture of the bonds between the end carbonyl groups and the naphthalene core, and occurs at incident electron energies above 2 eV. Possible chemical changes in condensed NTCDA molecules initiated by the DEA mechanism under conditions of electron transport through the film are discussed.

Low-energy electron transmission for the analysis of the interface barrier formation and the density of the unoccupied electronic states in the ultra-thin layers of fluorinated copper-phthalocyanine

“…There has been shown that the TCS fine structure is closely related to the density of the unoccupied electron states (DOUS) of the sample surface as if the peaks of the negative second derivative of the transmitted current -d 2 J(E)/dE 2 = -dS(E)/dE represent the DOUS peaks [21,24,25]. The quantum-chemical calculations were performed using the density functional theory (DFT) with the Gaussian software [26].…”

“…There has been shown that the as calculated VOEs provide underestimate values of the molecular orbital energies compared to the experimental values [28][29][30][31]. In order to correct the calculation results the following scaling procedure has been used successfully in a number of cases for the DOUS peak assignment in the films of small conjugated molecules [15,25,29,31,32]. For the π* molecular orbitals the scaled virtual orbital energies (SVOE) are given by the expression SVOE = (VOE+1.14)/1.24, and for the σ* molecular orbitals SVOE are given by the expression SVOE =(VOE+0.97)/0.79 [15,31].…”

Density of the unoccupied electronic states of the ultrathin films of the aziridinylphenylpyrrol substituted fullerene

“…The TCS fine structure S(E) is determined by the energy dependence of the elastic scattering of the incident electrons from the sample surface. There has been shown that the TCS measurements results provide information on the density of the unoccupied electron states (DOUS) of the sample surface as if the peaks of the negative second derivative of the transmitted current -d 2 J(E)/dE 2 = -dS(E)/dE correspond to the DOUS peaks of the surface under study [20,23,24].…”

Плотность Незаполненных Электронных Состояний Осажденных В Вакууме Пленок Диоктил-Замещенного И Дифенил-Замещенного Перилен-Дикарбоксимида

“…При этом в случае неупорядоченных поверхно-стей картина дифракционных рефлексов не наблюдается, а интегральный ток вторичных электронов может быть измерен. Зависимость S(E), тонкая структура спектров полного тока (ТССПТ), отражает изменения значения коэффициента упругого рассеяния падающих низкоэнер-гетических электронов от поверхности исследуемого образца, которые связаны с зависимостью плотности незаполненных электронных состояний (DOUS) от энер-гии, как было показано ранее для широкого круга неорганических и органических полупроводниковых ма-териалов [9,[15][16][17].…”