Y Lu

High resolution threshold photoelectron spectroscopy of rare gas dimers

Information on the structure of the ions of neon, argon, krypton and xenon dimers has been obtained using threshold photoelectron spectroscopy and synchrotron radiation under conditions of high resolution. Vibrational structure has been well resolved for the ground state of all these species thus allowing accurate values for the spectroscopic constants to be derived. Structure corresponding to excited states of the dimer ions dissociating to the 2P3/2,1/2 levels of the atomic ion have also been identified and their dissociation energies determined.

Ground and excited states of Xe+2 observed by high resolution threshold photoelectron spectroscopy of Xe2

Threshold photoelectron spectra of the xenon dimer have been observed with a resolution of 2 meV in the wavelength range 920–945 A and 1022–1112 A using the penetrating field technique and synchrotron radiation. Threshold photoelectron bands associated with transitions to the A2 Σ+1/2u, B2 Π3/2g, C2 Π3/2u, C2 Π1/2u, and D2 Σ+1/2g states of Xe+2 have been identified. Vibrational structure associated with the C2 Π1/2u state has been observed for the first time and a new value of the D2 Σ+1/2g state ionization potential is reported.

Vibrational structure of the N+2 ground state observed by threshold photoelectron spectroscopy

The long vibrational progression of the ground state of N+2 was observed in a high resolution threshold photoelectron spectrum obtained using the penetrating field technique and synchrotron radiation. Vibrational states were observed up to v′=67 for the first time and the final vibrational level was deduced to be v′=77 from extrapolation. The complete molecular constants of this state were obtained and the entire potential curve was then drawn.

Single-photon ionization study of the vibrational structure in the ground state of Xe+2

The vibrationally resolved spectra of the ground state A 2 Sigma +u of Xe+2 were observed at wavelengths from 1023 AA to 1116 AA by using the method of single-photon ionization with synchrotron radiation as a light source. A long progression beginning at v=0 was clearly observed in the threshold electron spectra for the first time. The spectroscopic parameters for the ground state of Xe+2 (average mass=131.3, 131.3) calculated from the experimental data are: omega e=122.9 (+or-0.1) cm-1 omega e chi e=0.481 (+or-0.001) cm-1, the dissociation energy D0=7849 (+or-9) cm-1, the zero point energy 61.3 (+or-0.1) cm-1, Te=90 119 (+or-8) cm-1, and the adiabatic ionization potential 90 170 (+or-8) cm-1. Autoionizing Rydberg series were found and assigned to converge to the C 2 Pi 32u/ and B2 Pi 12g/ states of Xe+2.

THRESHOLD PHOTOELECTRON SPECTRUM OF O2 IN 31-34 EV REGION

Abstract High resolution threshold photoelectron spectra of O 2 were obtained in the region of 31–34 eV. Three vibrational progressions were observed. These structures are assigned to two ionic Rydberg states converging to the O 2 2+ ground state and to a valence state.

Photoionization of Xe2, Xe3 and Xe4 in the 1024–1113 Å region

The mass spectra of Xen+ clusters (n=2−13) were recorded using a supersonic beam and an ion time-of-flight mass analyser. The yield of Xe2+, Xe3+ and Xe4+ cluster ions was measured with a resolution of 0.1 Å (≈1 meV) in the 1024–1113 Å (11.1–12.1 eV) region. Autoionizing Rydberg series of Xe2 converging to theC2Π3/2u state of Xe2+ were observed in the spectrum of Xe2+. The photoionization yield of Xe3+ and Xe4+ ions each displayed similar broad features that contained no fine structure corresponding to vibrational states. The broad features were assigned to autoionizing Rydberg series by analogy with the dimer ion spectrum.

Post-collision interaction effects induced by Auger cascades following Xe L1-shell photoionization

Abstract Yield spectra of multiply charged ions have been measured by threshold electron-ion coincidence spectroscopy near the Xe L 1 -shell photoionization region. These spectra exhibit asymmetric and broadened profiles of post-collision interaction effects induced by multi-step Auger decays in Auger cascades following Xe L 1 -shell photoionization. The peak shifts of the profiles increase gradually along with the increase of the charge states, but the peak widths are almost independent of the charge states. The spectral profiles are reproduced by a simple model based on the assumption that double Auger (Auger shake-off) decays reduce the effective number of steps in the Auger cascades.

High-resolution measurement of threshold photoelectrons with a time-of-flight spectrometer

A threshold photoelectron spectrometer combining electron time-of-flight and angular discrimination was constructed. The time-of-flight was measured using synchrotron radiation operating in single-bunch mode. Positioning of two time windows followed by substraction of their intensities allowed near-zero-energy electrons to be measured with high resolution. The resolution of the threshold electron spectrometer attained 1 meV for Xe and 1.7 meV for Ar.