Study of the electronic structure of pyridine by synchrotron photoelectron spectroscopy

Photoelectron and threshold photoelectron valence spectra of pyridine

“…Vertical values are marked with lines on the PES spectra in Figures 3-7, bottom panels. The nomenclature for labelling the states followed that proposed by Clementi [9], although various authors have different recommendations for the order of the molecular orbitals (see for example Moghaddam et al [17]). The data presented here is not only in an excellent agreement with the previous results, but also, due to high resolution of present experiment, it was possible to assign some new adiabatic ionization energies and resolve bands that previously appeared as one feature.…”

“…This simple aromatic azabenzene has been extensively studied in the past with respect to both its vibrational [6][7][8] and electronic structure [9] by experimental [10][11][12][13][14] and computational [15][16][17][18] approaches. Moreover, low-lying Rydberg states have also been examined for this molecule [19,20].…”

Ionization of pyridine: Interplay of orbital relaxation and electron correlation

“…To address this issue, in Table V we list the results for the four lowest vertical ionization energies obtained in the present work using different computational approaches, as well as those from previous studies. 35,40,42,46 As can be seen, the difficulty arises mainly from the large variation in the estimates for the nitrogen LP orbital, 7a 1 (σ N LP ), whose ionization energy depends strongly on the method used. At the highest level of theory (EOM-IP-CCSDT) employed in the present work, the 7a 1 (σ N LP ) 1 state is predicted to lie vertically below the 1a 2 (π) 1 state by 0.12 eV.…”

“…The shifts in the HF ionization energies are non-uniform, and are much larger for the n-levels than for the -levels. This effect is more pronounced in the propagator results 35,47,48,50,[53][54][55][56][57][58][59] than in those employing the EOM-IP-CC approach. 51 Previously, the ionization of pyridine has been studied theoretically by Suzuki and Suzuki, 41 using the continuum multiple scattering X (CMS-X) method, by Wan et al, 42 and Kitao and Nakatsuji, 43 using the SAC-CI method, and by Plashkevych et al 44 using…”

“…The ionization spectrum of pyridine has also been treated using many-body Green's function techniques. 35,47,48 A comprehensive review of the corresponding experimental work, carried out prior to 1988, has been provided by Innes et al 24 Many of these early studies focused on identifying the molecular orbitals giving rise to the first two bands in the photoelectron spectrum. The outermost band in the HeI excited photoelectron spectrum, [25][26][27][28][29][30] observed at binding energies between 9.2 and 10.2 eV, is predicted to correspond to ionization from the 7a 1 (σ N LP ) and 1a 2 () orbitals.…”