the rod is continuously translated and rotated by a stepper motor nd:yag laser (532 nm, 3-5 ns,...
DESCRIPTION
…undergo supersonic expansion and are skimmed into beam torr diffusion pump turbo pump turbo pump turbo pump Fullerenes react with carbon species in the vapourisation zone, then exit reaction channel the ions which enter the ion optics, where they are acuumulated in the central octopole segment After 3-10 single laser shot accumulations, the ions are transferred to the ICR cell, which is located within in the bore of a 9.4 tesla superconducting magnet. Under the influence of the high magnetic field, the ions exhibit cyclotron motion. The ions induce a current on electrodes, which is detected as an “image current” in the time domain, and then the signal is converted to the frequency domain by an FT. Thus, the mass of the ion is detected as a frequency.TRANSCRIPT
The rod is continuously translated and rotated by a stepper motor
Nd:YAG laser (532 nm, 3-5 ns, 5mj/pulse) vaporises the target rod by a single pulse/shot
Valve emits a helium pulse Fullerenes react
with carbon vapor (C, C2) in the “clustering zone”. Then, the gas exits the channel and undergoes a supersonic expansion to create a cooled, molecular beam
fullerene-coatedgraphite target rod
Cluster Source Block
accumulation octopole
target rod skimmer
transfer octopole
ICR cell
stepper motor
pulsed valve
10-7 torr
diffusion pump
10-7
turbo pump
10-8
turbo pump
10-10
turbo pump
pulsed valve
source
…undergo supersonic expansion and are skimmed into beam
10-7 torrdiffusion pump
10-7
turbo pump
10-8
turbo pump
10-10
turbo pump
Fullerenes react with
carbon species in the
vapourisation zone, then exit
reaction channel
the ions which enter the ion optics, where they are acuumulated in the central octopole segment
After 3-10 single laser shot accumulations, the ions are transferred to the ICR cell, which is located within in the bore of a 9.4 tesla superconducting magnet. Under the influence of the high magnetic field, the ions exhibit cyclotron motion. The ions induce a current on electrodes, which is detected as an “image current” in the time domain, and then the signal is converted to the frequency domain by an FT. Thus, the mass of the ion is detected as a frequency.
Q: How do you stop the pulse of ions in the accumulation trap A: The ions are confined radially by an oscilating radiofrequency within in octopole, and axially by voltages at the ends of the “accumulation octopole:.
Answer to questions from email.
Q: How many pulses do you need to accumulate?A: A single laser shot is used vaporize the target during a single Helium pulse. Ten singe laser shot + He pulse are used to accumulate ions.
Q:How do you decide when to transfer them.A: After the final laser shot, a voltage at the “back” of the accumulation octopole switched, and the ions are transferred to the ICR cell. The switching of the voltage is controlled by the computer program interface.
Q: How many runs do you need in general for an average result?A: 3 time-domain aquisitions are averaged for when “growing” a preformed fullerene…….the signal is extremely strong.And 10 time-domain acquisitions are averaged when form endohedrals from a graphite-metal target. Thus, up to 10 time-domain acquisitions are averaged.
Answer to questions from email.
Fullerenes react with carbon vapor in the “clustering zone”, then the gas exits the channel and undergoes a supersonic expansion. As the clusters move from a region of high pressure through a small orifice into a high vacuum, they undergo a supersonic expansion. The random thermal energy of the clusters is converted into a directed motion (creating a cooled, molecular beam in which very few collisions occur) toward the skimmer and the ions subsequently enter the ion optics where they are accumulated and then transferred to the ICR cell for detection.