Journal of Electron Spectroscopy and Related Phenomena 105 (1999) 99–112 www.elsevier.nl / locate / elspec Computational study of (e,2e) electron momentum spectroscopy and Penning ionization electron spectroscopy for molecular nitrogen a, a a a b b * S.X. Tian , X.J. Chen , C.K. Xu , K.Z. Xu , L.F. Yuan , J.L. Yang a Department of Modern Physics, University of Science and Technology of China, Hefei, P .O. Box 4, Anhui 230027, People’ s Republic of China b Open Laboratory of Bond Selective Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People’ s Republic of China Received 15 September 1998; received in revised form 29 April 1999; accepted 4 May 1999 Abstract The electron distributions of the outer valence orbitals of molecular nitrogen (N ): 3s ,1p and 2s , are studied by 2 g u u density functional method (DFT-B3LYP) calculations with the 6231G, 62311G, 623111G, and 623111G* basis sets, as well as at the self-consistent field Hatree 2Fock (SCF-HF) and the fourth-order Møller–Plesset (MP4) level calculations. The results obtained at the B3LYP/623111G and B3LYP/623111G* levels give good descriptions for the published experimental (e,2e) electron momentum spectra (Cook et al., Chem. Phys. 141 (1990) 211), and present a reasonable interpretation to the published Penning ionization electron spectra (Hotop et al., J. Electron Spectrosc. Relat. Phenom. 16 (1979) 213; Ohno et al., J. Am. Chem. Soc. 105 (1983) 4555, etc.) for the outer valence orbitals of N . Here the properties 2 of (e,2e) electron momentum spectroscopy (EMS) and Penning ionization electron spectroscopy (PIES) are compared and discussed in detail, and the interconnections between the momentum space electron distributions observed in EMS and the exterior electron distributions observed in PIES for outer valence orbitals of N are analyzed at last.  1999 Elsevier 2 Science B.V. All rights reserved. Keywords: Molecular nitrogen; Electron density; (e,2e) Electron momentum spectroscopy; Penning ionization electron spectroscopy; Ab initio; Density functional method 1. Introduction been supported by a vast accumulation of experi- ments, such as photoelectron spectroscopy with an Molecular orbital (MO) is an important concept of ultraviolet (UPS) or an X-ray source (XPS or the quantum theory, which is applied widely and ESCA), X-ray or g-ray Compton scattering, high successfully in quantum chemistry to various prob- energy electron scaterring, positron annihilation, lems. It is usually obtained by self-consistent field Penning ionization electron spectroscopy (PIES) and (SCF) calculation with linear combination atomic (e,2e) electron momentum spectroscopy (EMS), etc. orbitals (LCAO) approximation [1]. This method has It is interesting that study of atomic and molecular electron distributions can provide a good visual description for electronic structures of atoms and *Corresponding author. E-mail address: sxtian@mail.ustc.edu.cn (S.X. Tian) molecules. X-ray or g-ray Compton scattering, high 0368-2048 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0368-2048(99)00035-3