scholarly journals Characterization of Ground State Neutral and Ion Transport During Laser Ablation of 1:2:3 Superconductors by Transient Optical Absorption Spectroscopy

1989 ◽  
Vol 169 ◽  
Author(s):  
David B. Geohegan ◽  
Douglas N. Mashburn
Keyword(s):  
Laser Ablation ◽  
Optical Absorption ◽  
Ground State ◽  
Velocity Component ◽  
Film Growth ◽  
Growth Conditions ◽  
Optical Absorption Spectroscopy ◽  
Low Velocity ◽  
Ion Probe ◽  
Order Of Magnitude

AbstractOptical absorption in the plume produced by excimer laser ablation of Y1Ba2Cu3O7‐x under film growth conditions has been observed for the first time and used to characterize the transport of ground state Y, Ba, and Cu neutrals as well as Y+ and Ba+ ions. Spatially and temporally resolved absorption measurements (0.6 mm, 20 ns resolution) indicate significant ground state number densities at times following the laser pulse that are up to an order of magnitude longer than the duration of fluorescence from excited states. Time‐of‐flight absorbance profiles result in velocity distributions that are broadened significantly toward lower velocities and reveal a low velocity component (<10 5 cm s_1) to the ablation process which is not observed using emission spectroscopy. Electric ion probe measurements of the time dependence of Y+ ions confirm the existence of the new, slow velocity component. Electron densities >1016 cm‐3 in the white plasma close to the pellet have been estimated using spectrally broadened emission lines. The effects of oxygen ambient pressures and the detection of YO, BaO, and CuO also are reported. This technique is applicable as an situ monitor of the kinetic energy of ablated species during low temperature deposition of epitaxial 1:2:3 superconducting thin films.

Spectroscopic and Ion Probe Characterization of the Transport Process Following Laser Ablation of Yba2Cu3Ox

1990 ◽  
Vol 191 ◽  
Author(s):  
David B. Geohegan ◽  
Douglas N. Mashburn
Keyword(s):  
Laser Ablation ◽  
Ground State ◽  
Film Growth ◽  
Laser Energy ◽  
High Energy ◽  
Film Deposition ◽  
Oxygen Absorption ◽  
Total Charge ◽  
Laser Plume ◽  
Ion Probe

ABSTRACTSpatial and temporal measurements of the optical absorption, optical emission and ion probe response in the ablation plume formed following pulsed 248 nm irradiation of Y1Ba2Cu3Ox are reported over laser energy densities from near threshold into the film growth regime. Time of flight absorbance-velocity profiles in vacuum indicate the formation and acceleration of a plasma front, with ions leading neutrals on the edge of the expanding plume. Ion probe screening measurements show that the laser plume is a well-shielded plasma with Debye lengths <10 μm at film deposition distances. Velocity distributions and estimates of ground state Ba+, Ba, Y+, and Y densities indicate that the populations of the ions outnumber those of the neutrals at high energy densities in vacuum. Measurements of the slowing of the plasma front and attenuation of the total charge reaching the substrate are reported for laser ablation in background pressures of oxygen. Absorption by ground state YO and BaO in the region close to the pellet indicates oxide densities ˜5 × 1013 cm−3 close to the pellet.

Electron paramagnetic resonance, optical and magnetic studies of Tb 3+ in lanthanide nicotinate dihydrates

1987 ◽  
Vol 413 (1845) ◽  
pp. 515-528 ◽  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Optical Absorption ◽  
Ground State ◽  
Zeeman Effect ◽  
Optical Absorption Spectroscopy ◽  
Site Symmetry ◽  
Magnetic Studies ◽  
Paramagnetic Resonance ◽  
Defect Sites ◽  
Electron Paramagnetic

Optical absorption and fluorescence, magnetic susceptibility and electron magnetic resonance experiments have been made of Tb 3+ , 4f 8 , ions in lanthanide nicotinate dihydrate single crystals. Optical absorption spectroscopy in undiluted terbium nicotinate dihydrate (TbND) indicates that the ground state of Tb 3+ , 7 F 6 , is a singlet exhibiting a quadratic Zeeman effect, and this is confirmed by the observation of a temperature-independent Van Vleck paramagnetism below 4.2 K. This is what one would expect for a non-Kramers ion in a crystal field of no symmetry. In spite of this, electron paramagnetic resonance (epr) is observed from Tb 3+ ions both in dilute LaND containing 0.01 mole fraction of Tb and in TbND. In the dilute material, in spite of the absence of site symmetry, the results show a nearly degenerate non-Kramers doublet with a g value of 17.2(8), close to the maximum possible value of 12 g j ; the ground state must therefore be predominantly M j = ±6. The epr in TbND arises from some type of defect site involving two interacting dissimilar Tb 3+ ions. The spectrum of Tb 3+ ions observed by optical fluorescence is also attributed to defect sites.

Effect of growth conditions upon the phase transition and optical absorption edge in CuInP2S6 crystals

1999 ◽  
Vol 4 (0) ◽  
pp. 131-138
Author(s):  
І. П. Студеняк ◽  
Д. Ш. Ковач ◽  
В. В. Митровцій ◽  
М. І. Гурзан ◽  
О. А. Микайло ◽  
...  
Keyword(s):  
Phase Transition ◽  
Optical Absorption ◽  
Absorption Edge ◽  
Growth Conditions ◽  
Optical Absorption Edge
Sign in / Sign up

Export Citation Format

Share Document