A high-intensity, pulsed supersonic carbon source with C({sup 3}{ital P}{sub {ital j}}) kinetic energies of 0.08--0.7 eV for crossed beam experiments
- Department of Chemistry, University of California and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
An enhanced supersonic carbon source produces carbon atoms in their C({sup 3}{ital P}{sub {ital j}}) electronic ground states via laser ablation of graphite at 266 nm. The 30 Hz (40{plus_minus}2) mJ output of a Nd-YAG laser is focused onto a rotating graphite rod with a 1000 mm focal length UV-grade fused silica plano-convex lens to a spot of (0.5{plus_minus}0.05) mm diameter. Ablated carbon atoms are subsequently seeded into helium or neon carrier gas yielding intensities up to 10{sup 13} C atoms cm{sup {minus}3} in the interaction region of a universal crossed beam apparatus. The greatly enhanced number density and duty cycle shift the limit of feasible crossed beam experiments down to rate constants as low as 10{sup {minus}11}--10{sup {minus}12} cm{sup 3} s{sup {minus}1}. Carbon beam velocities between 3300 and 1100 m s{sup {minus}1}, with speed ratios ranging from 2.8 to 7.2, are continuously tunable on-line and {ital in} {ital situ} without changing carrier gases by varying the time delay between the laser pulse, the pulsed valve, and a chopper wheel located 40 mm after the laser ablation. Neither electronically excited carbon atoms nor ions could be detected within the error limits of a quadrupole-mass spectrometric detector. Carbon clusters are restricted to {similar_to}10% C{sub 2} and C{sub 3} in helium, minimized by multiphoton dissociation, and eliminating the postablation nozzle region. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- OSTI ID:
- 165924
- Journal Information:
- Review of Scientific Instruments, Vol. 66, Issue 12; Other Information: PBD: Dec 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Separation of the {ital sp}{sup 3} and {ital sp}{sup 2} components in the C1{ital s} photoemission spectra of amorphous carbon films
Crossed-beam reaction of C({sup 3}{ital P}{sub {ital j}}) with C{sub 2}H{sub 2}({sup 1}{summation}{sup +}{sub g}): Observation of tricarbon-hydride C{sub 3}H