Shunji Katsumata

UV photoelectron spectra and sum rule consideration: Out-of-plane orbitals of unsaturated compounds with planar-skeleton structure

Abstract He(l) photoelectron spectra are presented for various planar unsaturated aliphatic compounds such as mono- and di-methyl substituted ethylenes, alkyl aldehydes, chloro-substituted aldehydes, ketones and alkyl acids. Each photoelectron spectrum is resolved into individual bands by considering the band shape, the relative intensity and the number of p-type localized MOs (LOs). The sum rule previously proposed on vertical ionization energies by the present authors is applied to the photoelectron bands associated with out-of-plane LOs. In each compound, a partial sum P (a″) is obtained over all the out-of-plane LOs and it is shown that the calculated P (a″) value is in good agreement with the experimental one which may be obtained by an appropriate sum of vertical ionization energies with negative signs.

Excited-state photoelectron spectra of the one-photon forbidden C3IIg rydberg state of molecular oxygen

Abstract The Rydberg C 3 II g , state of molecular oxygen, which is one-photon forbidden from the ground electronic state, has been studied by means of (2 + 1) multiphoton ionization (MPI) ion-current and photoelectron spectroscopic techniques in the laser wavelength region 287–289 nm. Excitedstate photoelectron spectra have been observed at different rotational levels of the C 3 Π g v = 2 state of O 2 , and show marked deviation from the Franck-Condon distribution generally expected in ionization of Rydberg electrons. Namely, in addition to main photoelectron peaks due to Δ v = 0 transitions, other vibrational peaks are also observed with considerable intensities. The v + = 2 photoelectron peak shows different angular dependence from the other vibrational peaks. The rotational structure in the MPI ion-current spectrum of O 2 is well interpreted in terms of the rotational constants of the X 2 Π g ground electronic state of O 2 + .

Photoelectron spectroscopic study of hydrazine

Abstract The photoelectron spectrum of hydrazine having a skew configuration (C 2 ) was analyzed by CNDO/2 and MINDO/2 methods, and it was found that valence orbitals may be assigned to the 3a(π + , 3b(π − ), 4a(σ), 4b(n − ), and 5a(n + )) orbitals in this order, where n, α, and π denot the Nue5f8N bonding orbital, and the NH 2 pseudo-π orbital, respectively, and the + and — combinations mean symmetric and antisymmetric with respect to the C 2 axis. The splitting between the two nonbonding bands (corresponding to 4b and 5a) can be interpreted mainly in terms of a through-bond interaction and the ca A consideration of sum rule on vertical ionization energies is discussed, in support of the above orbital assignment.

Photoelectron angular distribution of simple molecules at 30.4 nm photons

Abstract The asymmetry parameter (β) of angular distribution of photoelectrons has been obtained with He(I) (58.4 nm) and He(II) (30.4 nm) resonance radiation for several simple compounds (N2, O2, H2O, CO2 and CS2), in order to examine how the β value depends on the excitation energy. It has been found that on going from He(I) to He(II) radiation the energy dependence of β for the nonbonding orbitals of triatomic molecules is similar to that obtained theoretically by Manson for the corresponding atomic p shells. For N2 it has also been found that there is essentially no difference in β values between two vibrational peaks (υ′= 0 and 1) of the first ionisation band in the He(II) spectrum, whereas in the He(I) spectrum an anomalous variation is observed in the β values between the two peaks as originally indicated by Carlson. These results support the interpretation of the autoionisation mechanism suggested by Mintz and Kuppermann.

Photoelectron angular distribution and assignments of photoelectron spectra of nitrogen dioxide, nitromethane and nitrobenzene

Abstract Photoelectron bands closely associated with the NO2 group have been identified for CH3NO2 and C6H5NO2 in the gas phase by determining the asymmetry parameter (β) of the photoelectron angular distribution with HeI and NeI radiation. For NO2, β values for the 3,1 A2 and 3,1 B2 ionic states have been obtained which are associated with the out-of-plane NO2 orbitals. Ab initio SCF MO CI calculations of ionic states have been carried out for NO2 and CH3NO2. For CH3NO2, three ionization bands observed with different β values (0.08, 0.20 and 0.14 for NeI radiation), appearing in the region below ≈ 12 eV have been assigned to the (n+O) −1, (π2)−1 and (n−O)−1 ionic states. For C6H5NO2, on the basis of ab initio SCF MO calculations, it has been concluded that, besides the first two bands with β(HeI) = 0.7–0.8 previously assigned to the π orbitals of the benzene ring, the next three bands with a β(HeI) value of 0.11 appearing in the 10.7–12.0 eV region are assigned to the NO2 orbitals.

Photoelectron spectra and sum rule consideration: Effect of chlorine substitution on ionization energies for chloroethanes, chloroacetaldehydes and chloroacetyl chlorides

Abstract He(I) photoelectron spectra are reported for various series of chlorine-substituted compounds: (a) CH 3 CH 3− m Cl m , (b) CH 3− m Cl m CCl 3 , (c) CH 3− m Cl m CHO and (d) CH 3− m Cl m COCl, where m = 1, 2 and 3. In each series it is shown that the total sum of vertical ionization energies over all p-type localized molecular orbitals (LOs) has an excellent linear relationship to the number of substituted chlorine atoms. The differences in the total orbital energy sum by successive chlorine substitutions are found to be 26.7 eV for series a and b and 27.2 eV for series c and d, yielding the corresponding experimental σ CCl , energies useful for sum rule considerations. The photoelectron spectra of the chloro compounds studied are interpreted with the help of the sum rule as well as CNDO/2 calculations. Orbital correlation diagrams have been constructed for these compounds.

Ionic photodissociation and ionic photosensitized dissociation of charge-transfer complexes

Abstract Flash spectroscopic and kinetic studies have been carried out on the charge-transfer complex of tetracyanoethylene with tetrahydrofuran in a liquid paraffin solution at room temperature. The rise and decay curves in transient electronic absorption intensity have been observed with a common rate constant, corresponding to the anion radical of tetracyanoethylene and the triplet state of the charge-transfer complex, respectively. From the kinetic analysis it has been concluded that the ionic photodissociation of this complex takes place in its lowest excited triplet state. This dissociation mechanism has also been confirmed by employing a triplet energy transfer technique with which “ionic photosensitized-dissociation” phenomenon is observed. Furthermore, a few other examples of ionic photosensitized-dissociation are demonstrated in rigid glasses with typical weak charge-transfer complexes whose photodissociation processes are well-known.

Photoelectron spectra and orbital assignments by sum rule consideration: Ethyl and n-propyl fluorides

Abstract The He I photoelectron (PE) spectra of C 2 H 5 F and n-C 3 H 7 F have been obtained. The PE spectra indicate that the first ionization potentials are about 0.4 eV higher than those of the parent alkanes owing to the inductive effect of fluorine. All the PE bands obtained here have been interpreted in terms of appropriate p -type localized MOs using the sum rule described previously by the authors. Orbital energy diagrams involving the inductive effect of fluorine are illustrated. The semi-empirical CNDO/2 and MINDO/2 methods were also employed to help confirm the present orbital assignments.

Photoelectron spectroscopic study of hydroxylamine (NH2OH) and o-methylhydroxylamine (NH2OCH3)

Hei photoelectron spectra of hydroxylamine and o‐methylhydroxylamine in the gaseous phase have been measured below 20 eV, and have been resolved into five and seven ionization bands, respectively, corresponding to p‐type molecular orbitals. On the basis of available ab initio MO calculations by Fink et al., the p‐type photoelectron bands of hydroxylamine have well been interpreted in terms of a trans staggered form already known as the most stable conformation in the gaseous phase. Orbital assignments on the p‐type bands of o‐methylhydroxylamine have been made on the basis of CNDO/2 calculations which were also carried out in the present work, except for the first two bands whose assignments were based on orbital‐interaction considerations. An ionization‐energy sum rule proposed previously has also been tested for the compounds studied here.

Photoelectron angular distribution of H2S measured with NeI to HeII resonance lines

Abstract The asymmetry parameter (β) of the photoelectron angular distribution for H 2 S has been measured with NeI, NeII and HeII resonance radiation The present results on the energy dependence of β for each ionic stale are in excellent agreement with theoretical results obtained by Roche et al with an Xα scatteimg wave method