Dissociation processes of Kr2(+) and Kr3(+) studied by threshold photoelectron-photoion coincidence measurements.

A time-of-flight (TOF) ion mass spectrum in coincidence with threshold photoelectrons was measured in the photon energy region between the first and second dissociation limits of Kr2(+) to examine the decay processes of the Kr2(+) II(1/2u) state. The measured TOF spectrum reveals that Kr+ fragment ions are produced through dissociation of the repulsive I(1/2g) state, which can be formed by the decay process of the II(1/2u) state accompanied with emission of photons. The potential-energy curve of the I(1/2g) state is deduced with detailed analysis of the observed TOF spectrum, in which the radiative lifetime of the II(1/2u) state was also derived to be 2.5 micros. Additionally, evidence of the dissociation process of Kr3(+) ions was obtained in the same photon energy region, where the dominant channel is Kr3(+) --> Kr2(+) + Kr.

Dynamical Auger emission induced by multistate vibronic coupling in the core-excited states of the BCl3 molecule.

The Auger emission following the resonant excitation of the BCl3 molecule has been investigated using monochromatized synchrotron radiation. The B 1s excitation to the unoccupied Anti-bonding 4e(') orbital enhances the shoulder structure in the low kinetic energy side of the photoemission from the 2e(') valence bonding orbital. Based on a series of quantum mechanical calculations, this shoulder structure is interpreted as the dynamical Auger emission which reflects the B-Cl stretching nuclear motion and appears as a result of the purely multistate vibronic coupling effect among the Jahn-Teller split B 1s(-1)4e(') E' states and the closely lying B 1s(-1)3a(')(1) A'1 state.

Pulsed-Field Ionization Zero-Kinetic-Energy Photoelectron Spectra of Ar(2).

The pulsed-field ionization (PFI) zero-kinetic-energy (ZEKE) photoelectron spectra of Ar(2) were measured between 117 000 cm(-1) (14.5 eV) and 128 300 cm(-1) (15.9 eV) using the penetrating field technique and synchrotron radiation at resolutions of up to 1 meV. The A(2)Sigma(+)(1/2u) ground state and B(2)Pi(1/2g) and C(2)Pi(3/2u) excited states were assigned to those spectra. The first adiabatic ionization potential of Ar(2) was determined to be 14.4572 +/- 0.0007 eV. A Le Roy-Bernstein plot and a Birge-Sponer plot were used to determine the dissociation limit of the A(2)Sigma(+)(1/2u) ground state. The vibrational level of the C(2)Pi(3/2u) excited state was observed for the first time. The effective lifetime for high-n Rydberg states converging on the vibrational levels of the C(2)Pi(1/2u) excited state is estimated to be shorter than those of the A(2)Sigma(+)(1/2u), B(2)Pi(1/2g), and C(2)Pi(3/2u) states, because the spectrum could not be observed on the PFI-ZEKE experiment. The threshold photoelectron-photoion coincidence spectra of Ar(2) were also measured and compared with the spectra obtained from the PFI-ZEKE experiment. Copyright 1999 Academic Press.

High-resolution spherical grating monochromator for the undulator beamline (BL-16B) at the Photon Factory.

The design and performance of a 24 m high-resolution spherical grating monochromator (H-SGM) for the undulator beamline (BL-16B) at the Photon Factory are described. With three interchangeable gratings of 400, 900 and 2000 lines mm(-1), the H-SGM is designed to cover the photon energy range 40-600 eV. With a resolving power of approximately 2000 in the photon energy range 40-530 eV, more than 10(11) photons s(-1) have been measured. The best resolutions obtained so far, at a substantially lower photon flux, are greater than 10 000 at 250 eV and 8000 at 400 eV

New N2+ Electronic States in the Region of 23-28 eV

Threshold photoelectron spectra of N2+ were measured between 23.4 and 27.6 eV with high resolution and high intensity by using the penetrating field technique and synchrotron radiation. Five vibrational progressions were observed. The first of these progressions was the C2Sigmau+ state. The second progression was identified as the transition to the second state of 2Pig symmetry found by P. Baltzer, M. Larsson, L. Karlsson, B. Wannberg, and M. Carlsson (1992. Phys. Rev. A 46, 5545). The third progression, which was discovered by F. Merkt and P. M. Guyon (1993. J. Chem. Phys. 99, 3400), can be designated as the 2Sigmau- state by comparison with previous theoretical study (E. W. Thulstrup and A. Andersen, 1975. J. Phys. B 8, 965). The fourth and fifth progressions were designated as the 2Deltau and 2(2) Piu states by similar comparison with previous theories. Copyright 1997 Academic Press. Copyright 1997Academic Press