A quantitative investigation of emission from low temperature laser-induced YBa2Cu3Ox plasma plumes

Abstract

The effects of the electric field associated with a laserinduced pulsed discharge on the ablationgenerated plumes of YBa2Cu3O7−X

Electronic State Distributions of YBa2Cu3O7-x Laser-Ablated Plumes

“…These results are consistent with prior reported work on atomic electronic state distributions by Ying [91] and ElAstal [28,29]. It is also consistent with YO electronic state distributions measured by Weiner, [89] who noted nonequilibrium among YO spin-orbit, vibrational, and rotational temperatures, as well as non-equilibrium in the vibrational temperatures There are significant consequences to concluding the plume is not in LTE.…”

“…[9] Another line-ratio measurement was conducted by Harilal [91] With the exception of Ying's paper, [91] most of the published electronic temperature measurements have been obtained using line-ratio measurements. [8,10,[27][28][29]45] There is a risk to performing a calculation based on a ratio of two data points, in that a perturbation to one of the data points may skew the results more than if the calculation was performed by fitting a line through a greater number of data points. Several mechanisms may cause a significant error in a data point, resulting in a skewed result.…”

“…This now yields the expression The applicability of the LTE approximation to laser ablated plumes is not universally accepted. Some authors accept the LTE approximation without question, [27,46] some use the LTE approximation with reservations, using the Boltzmann representation merely as a compact method of describing the electronic state distribution, [28,91] while others flat out reject the validity of assuming LTE. [9] Early papers in the literature on the topic of electronic state distributions tended to take simple approaches using sparse data sets, and presented limited detail.…”

“…The method of electronic temperature measurements by line intensity ratios was extended by El-Astal, [28,29] The line-ratio approach was used by Apostol to measure plume temperatures near the ablation site. [9] Measurements were taken 200 nsec after ablation, and 1 mm above the target surface, yielding temperatures ranging from 0.6 to 1 eV.…”

“…[8,[27][28][29] Second, most of the prior work predated the discovery of significant self-absorption in the plume, [72,73] which could have significant consequences on electronic temperatures derived from line ratios if the self-absorption effect differs from line-to-line. Third, it has been asserted in the literature that temporal signal averaging effects may distort electronic temperatures calculated from spectral data if the plume temperature changes significantly during signal collection.…”