Tetsuya Fukuyama

Single |JΩMJ〉 state-selection of OH radicals using an electrostatic hexapole field

The focusing curve of the single quantum state |JΩMJ〉 = |1/2,1/2,1/2〉 of OH radicals was measured using the combined methods of state selection with an electrostatic hexapole of 1 m length, and detection by laser induced fluorescence for the OH(A ← X) transition at 308 nm. The observed focusing curve is a reliable test for the trajectory simulation since it only consists out of a single quantum state of molecules. The trajectory simulations including the Λ-type doubling effect could reproduce the observed focusing curves. The focusing curves for |JΩ> = |3/2,3/2〉, |5/2,3/2〉, and |7/2,3/2〉 were also measured. The results were compared with the trajectory simulations and discussed with the population of the contributed |MJ| states in the focusing curves.

Steric Effects in the Scattering of Oriented CH3Cl Molecular Beam from a Graphite Surface: Weak Interaction of Physisorption

We report results of a study on steric effects appearing in the scattering of an oriented CH(3)Cl molecular beam from highly oriented pyrolytic graphite (HOPG) surface at 300 K. Data presented here show that the scattered CH(3)Cl beam intensity measured at a fixed scattering angle clearly depends on the initial molecular orientation toward the HOPG surface. The scattered CH(3)Cl beam intensity for the CH(3)-end collision is larger than that for the Cl-end collision, suggesting that strong anisotropy of the interaction potential induces the molecular-orientation-dependent energy dissipation during transient trapping into the physisorption well.

Full characterization of an intense pulsed hyperthermal molecular beam

A molecular beam technique for generating an intense pulsed hyperthermal molecular beam (pulsed HTMB) was developed. The beam source consists of a pulse valve, a cooling-water bottle that protects the pulse valve from heat transfer of the high temperature nozzle, and a nozzle with a heater. The point was a pulse-valve operation with the high temperature nozzle which was 30-mm long and was made of pyrolytic boron nitride. The pulsed HTMB of HCl was practically generated. The total beam intensity of the pulsed HTMB was measured by a quadrupole mass spectrometer. It was determined that the beam intensity of the pulsed HTMB was two orders of magnitude larger than that obtained in continuous-HTMB conditions. The pulsed HTMB of HCl was fully characterized by means of (2+1) resonance-enhanced multiphoton ionization and ion time-of-flight techniques. We found that the velocity distribution of the pulsed HTMB was well expressed as supersonic molecular beams. At the highest nozzle temperature of 1400 K, the mean tr...

Electrostatic hexapole state selector: Honeycomb field for integrating intensity of oriented molecular beams

A type of electrostatic state selector that consists of seven sets of adjacent hexapole fields forming a honeycomb field has been developed in order to integrate intensities of seven oriented molecular beam lines. The cross section of the electric field is gradually diminished from the inlet to the outlet in order to sum up the seven molecular beam lines and focus on a focal point located 1000 mm downstream from the honeycomb field outlet. We first used nonfocusable noble gases: Ar and Kr to check the assembly alignment, and then we used the polar molecule of acetonitrile (CH3CN, μ=3.92 D) seeded in the noble gases to characterize the quantum state selectivity of the honeycomb field. We obtained the dependence of the focused CH3CN beam intensity on the honeycomb electrode voltages. We could reproduce the experimental focusing curve by use of a modified trajectory simulation applicable to the honeycomb electric field. The present beam character (i.e., rotational temperature and stream velocity) was confirm...

Kinetics and dynamics in physisorption of CH3Cl on HOPG: surface temperature and molecular orientation dependence

We report a study of kinetics and dynamics in physisorption of CH(3)Cl on a highly-oriented pyrolytic graphite (HOPG). Thermal energy atom scattering (TEAS) was used to probe the kinetics of thermal CH(3)Cl adsorption on HOPG during the coverage evolution. The desorption energy of CH(3)Cl on HOPG changes from 0.25 to 0.30 eV with increasing surface coverage, suggesting the attractive interaction between CH(3)Cl molecules on the surface. On the other hand, the oriented molecular beam scattering was used to monitor the dynamical interaction of CH(3)Cl with HOPG at zero coverage, demonstrating that the CH(3)Cl scattering intensity depends on the molecular orientation of the incident CH(3)Cl. The observed steric preference is not sensitive to the surface temperature. These results suggest that the moderate anisotropy in the interaction potential induces the molecular-orientation dependence of energy dissipation during the transient trapping into the physisorption well.

Stereospecific Control by Molecular Orientation

A new type of electrostatic state‐selector that consists of seven sets of adjacent hexapole fields forming a honeycomb field has been newly developed in order to integrate intensities of seven oriented molecular beam lines. We first used Ar gas to check the assembly alignment, and then we used the polar molecule of acetonitrile (CH3CN, μ=3.92 D) seeded in the noble gases to characterize the quantum state‐selectivity of the honeycomb field. We obtained the dependence of the focused CH3CN beam intensity on the honeycomb electrode voltages for the first time. We could reproduce the experimental focusing curve by use of a modified trajectory simulation applicable to the honeycomb electric field. The present beam character (i.e. rotational temperature and stream velocity) was confirmed to be maintained as same as the one of the original single beam.