Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110).
The angular and velocity distributions of desorbing product N(2) were examined over the crystal azimuth in steady-state NO+CO and N(2)O+CO reactions on Pd(110) by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N(2) desorption in both reactions splits into two directional lobes collimated along 41 degrees -45 degrees from the surface normal toward the [001] and [001] directions. Above 600 K, the normally directed N(2) desorption is enhanced in the NO reduction. Each product desorption component, as well as CO(2), shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.
A LEED STRUCTURAL STUDY OF THE CO INDUCED RECONSTRUCTION OF PD(110) - EVIDENCE FOR A MISSING ROW STRUCTURE
Abstract Molecularly adsorbed CO on Pd{110} has been shown (R. Raval et al., Chem. Phys. Lett. 167 (1990) 391, ref. [1]) to induce a substantial reconstruction of the surface in the coverage range 0.3 I ( E ) “fingerprinting” analysis of the CO/Pd{110}-(4 × 2) structure in order to establish the type of reconstruction induced in the metal surface. This study shows that the LEED I ( E ) profiles of the integral order and appropriate half-order beams of the CO/Pd{110}-(4 × 2) pattern closely resemble the I ( E ) profiles theoretically calculated for a Pd{110}−(1 × 2) missing-row structure. Additionally, there is a strong resemblance to the experimental LEED I ( E ) profiles for the Cs/Pd{110}-(1 × 2) structure which has also been shown to exhibit the missing-row structure. On the basis of this evidence we conclude that the CO/Pd{110}-(4 × 2) LEED pattern arises from a missing-row reconstruction of the Pd{110} surface which gives rise to a strong underlying (1 × 2) pattern plus a poorly ordered CO overlayer which produces weak, diffuse fourth-order spots in the LEED pattern.
DESIGN CONSIDERATION TO PPM KLYSTRONS FOR INDUSTRIAL LINAC
Toshiba has been developing the C-band and X-band Periodic Permanent Magnet (PPM) focused klystron in collaboration with KEK and manufactured prototypes for the JLC project. [1] The PPM klystron has an advantage to enhance the total efficiency as a result of eliminating the electric power for the focusing magnet. From experience on the development the PPM focused klystrons for the JLC project, we plan to apply the PPM focused klystron to the medical and industrial linac. The periodic magnet focusing scheme has some technical difficulties such as stop band voltage. To design the PPM klystron for the medical and industrial linac, it is necessary to give heed to electron beam instability; so that the tube parameters of the PPM focused klystrons have some constraints. The size of the accelerator system is substantially reduced if a PPM focused klystron is used. The majority of medical and industrial linacs use frequencies of S-band range. We discuss the availability of the S-band PPM focused klystron in this paper.