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Describes the development of an efficient electron time-of-flight selection scheme for high resolution pulsed field ionization photoelectron (PFI-PE) measurements using monochromatized multibunch undulator synchrotron radiation at the Advanced Light Source. PFI-PE bands; Spectral analysis; Advantage of synchrotron based PFI-PE experiments.

Describes the development of an undulator beamline for chemical dynamics experiments conducted at the Advanced Light Source facility in Berkeley, California. Description of the beamline; Characterization of the gas harmonic filter; Measurement of the flux from the white beam and monochromator branchlines; Determination of the off-plane Eagle monochromator resolution.

Focuses on high resolution threshold and pulsed field ionization photoelectron spectroscopy using multi-bunch synchrotron radiation. Resolution for threshold photoelectron measurements; Characteristics of the monochromatized vacuum ultraviolet beam at the chemical dynamics beamline; Photoionization-photoelectron apparatus.

Shows that state-selected O[sup +](sup 4]S[sup 0]), O[sup +]([sup 2]D[sup 0]) and O[sup +]([sup 2]P[sup 0]) reactant ion beams with high purities and usable intensities can be prepared for scattering experiments by controlling the collision energies for dissociative charge transfer collisions in a radio frequency multipole ion guide gas cell.

Integral collision-induced dissociation (CID) cross sections at center-of-mass (CM) energies ranging from threshold to 22 eV and product ion recoil velocity distributions are presented for O[sub 2][sup +]+Ne(Ar) collisions. The O[sub 2][sup +] ions are produced in an electron impact ion source and thus have ∼0.5 eV of vibrational energy. The O[sub 2][sup +]+Ne CID cross sections are observed at energies below the 0 K thermodynamic threshold of 6.66 eV, implying the possibility of significant vibrational effects. A second CID threshold is apparent at 9±1 eV. This is close to the charge-transfer (CT) threshold energy. No CT products are observed. The O[sub 2][sup +]+Ar CID cross section rises rapidly above a relative translational energy onset of 7.5±0.2 eV and reaches a maximum value of ∼0.8 Å2 at 14 eV (CM). A CT onset of 6.0±0.2 eV is observed which is close to the thermodynamic threshold for CID. The energy dependence of the CT cross section is very similar to the CID cross section except for a small step at energies where CID becomes efficient. The CID recoil velocity distributions near threshold are centered at the CM velocity and shift to forward preference at higher energies. The O[sub 2][sup +]+Ar CT recoil velocities are forward scattered near threshold and become centered with respect to the CM velocity at energies where competition with CID is apparent. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The vacuum ultraviolet (VUV) pulsed field ionization-photoelectron (PFI-PE) spectra for CO[sub 2] have been measured in the energy range of 17.2-19.0 eV, showing complex vibronic structures for the CO[sub 2][sup +](A [sup 2]Π[sub u] and B [sup 2]Σ[sub u][sup +]) states. The PFI-PE spectra for CO[sub 2][sup +](A [sup 2]Π[sub u] and B [sup 2]Σ[sub u][sup +]) are dominated by the v[sub 1][sup +] (symmetric stretching) vibrational progressions, and weak bands due to excitation of both even and odd quanta of the v[sub 2][sup +] (bending) and v[sub 3][sup +] (antisymmetric stretching) modes are observed in the VUV-PFI-PE spectra. The simulation of rotational contours resolved in the PFI-PE vibronic bands associated with excitation to CO[sub 2][sup +](A [sup 2]Π[sub 3/2,1/2u];v[sub 1][sup +]=0-5,v[sub 2][sup +]=0,v[sub 3][sup +]=0) and CO[sub 2][sup +](B [sup 2]Σ[sub u][sup +];0,0,0) has yielded accurate ionization energies for the formation of these states from CO[sub 2](X [sup 1]Σ[sub g][sup +]). Three-dimensional potential energy functions (PEFs) for CO[sub 2][sup +](B [sup 2]Σ[sub u][sup +]) have also been generated theoretically using the complete active space self-consistent field and internally contracted multireference configuration interaction methods. Based on these PEFs, vibrational energy levels for CO[sub 2][sup +](B [sup 2]Σ[sub u][sup +]), together with the Franck-Condon factors for their formation from CO[sub 2](X [sup 1]Σ[sub g][sup +]), have been calculated. With the guide of these theoretical predictions, the vibrational bands resolved in the PFI-PE spectrum for CO[sub 2][sup +](B [sup 2]Σ[sub u][sup +]) have been satisfactorily assigned. This assignment reveals the nature of many vibrational PFI-PE bands as originated from anharmonic resonance interactions and members of Fermi polyads. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The vacuum ultraviolet pulsed field ionization-photoelectron (PFI-PE) spectra for CO[sub 2] have been measured in the energy range of 13.6-14.7 eV, revealing complex vibronic structures for the ground CO[sub 2][sup +](X [sup 2]Π[sub g]) state. Many vibronic bands for CO[sub 2][sup +](X [sup 2]Π[sub g]), which were not resolved in previous photoelectron studies, are identified in the present measurement based on comparison with available optical data and theoretical predictions. As observed in the HeI photoelectron spectrum of CO[sub 2], the PFI-PE spectrum is dominated by the symmetry allowed ν[sub 1][sup +] (symmetric stretch) vibrational progression for CO[sub 2][sup +](X [sup 2]Π[sub g]). However, PFI-PE vibronic bands due to excitation of the symmetry disallowed ν[sub 2][sup +] (bending) and ν[sub 3][sup +] (asymmetric stretch) modes with both odd quanta, together with the symmetry allowed even quanta excitations, are clearly discernible. The simulation of rotational contours resolved in PFI-PE vibronic bands associated with excitation to the (ν[sub 1][sup +]=0-1, ν[sub 2][sup +]=0-2, ν[sub 3][sup +]=0) vibrational levels has yielded accurate ionization energies for the formation of these vibronic states from CO[sub 2](X [sup 1]Σ[sub g][sup +]). © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have obtained rotationally resolved pulsed-field ionization photoelectron (PFI-PE) spectra for O[sub 2] in the energy range of 17.05-18.13 eV, covering the ionization transitions O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]=0-12,N[sup +])←O[sub 2](X [sup 3]Σ[sub g][sup -],v[sup ″]=0,N[sup ″]). Although these O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]) PFI-PE bands have significant overlaps with vibrational bands for O[sub 2][sup +](a [sup 4]Π[sub u]) and O[sub 2][sup +](X [sup 2]Π[sub g]), we have identified all the O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]=0-12) bands by simulation of spectra obtained using supersonically cooled O[sub 2] samples with rotational temperatures approx. 20 and 220 K. While these v[sup +]=0-12 PFI-PE bands represent the first rotationally resolved photoelectron data for O[sub 2][sup +](A [sup 2]Π[sub u]), the PFI-PE bands for O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]=9 and 10) are the first rotationally resolved spectroscopic data for these levels. The simulation also allows the determination of accurate ionization energies, vibrational constants, and rotational constants for O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]=0-12). The analysis of the PFI-PE spectra supports the conclusion of the previous emission study that the O[sub 2][sup +](A [sup 2]Π[sub u],v[sup +]=9 and 10) states are strongly perturbed by a nearby electronic state. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have obtained rotationally resolved pulsed field ionization-photoelectron (PFI-PE) spectra of O[sub 2] in the energy range of 16.0-18.0 eV, covering ionization transitions O[sub 2][sup +](a [sup 4]Π[sub u], v[sup +]=0-18,J[sup +])←O[sub 2](X [sup 3]Σ[sub g][sup .], v[sup ″]=0,N[sup ″]). Although these vibrational PFI-PE bands for O[sub 2][sup +](a [sup 4]Π[sub u], v[sup +]) have significant overlaps with those for O[sub 2][sup +](X [sup 2]Π[sub g]) and O[sub 2][sup +](A [sup 2]Π[sub u]), we have identified all O[sub 2][sup +](a [sup 4]Π[sub u], v[sup +]=0-18) bands by simulation of spectra obtained using supersonically cooled O[sub 2] samples with rotational temperatures approx. 20 and 220 K. While the v[sup +]=4-18PFI-PE bands represent the first rotationally resolved photoelectron data for O[sub 2][sup +](a [sup 4]Π[sub u]), the PFI-PE bands for O[sub 2][sup +](a [sup 4]Π[sub u], v[sup +]=10-18) are the first rotationally resolved spectroscopic data for these levels. The simulation also allows the determination of accurate ionization energies, vibrational constants, and rotational constants for O[sub 2][sup +](a [sup 2]Π[sub u], v[sup +]=0-18). The observed intensities of spin-orbit components for the majority of O[sub 2][sup +](a [sup 2]Π[sub u], v[sup +]) vibrational bands are in accordance with the forced spin-orbit/rotational autoionization mechanism. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A letter to the editor about images from routine carpal tunnel decompression is presented to remind surgeons what to look for when conducting a carpal tunnel decompression.

We have demonstrated that the time-of-flight (TOF) selection method for pulsed field ionization (PFI) photoelectron detection [Jarvis et al., Rev. Sci. Instrum. 70, 2615 (1999)] can also be applied for the detection of PFI-photoions (PFI-PIs) using the two-bunch synchrotron radiation at the Advanced Light Source. By employing the supersonic beam technique to lower the translational temperature of the sample gas, we show that background prompt ions formed in direct and spontaneous autoionization processes arrive at the ion detector in a pattern similar to that of the vacuum ultraviolet light bunches. The PFI-PIs formed at dark gaps can be designed to arrive at the detector in between adjacent prompt ion peaks, enabling the gating of the PFI-PI signal with only minor contamination from background prompt ions. This experiment has revealed important considerations for the design of a general TOF selection scheme for PFI-PI detection using synchrotron radiation. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]