Spectroscopic studies in the far ultraviolet (80-200nm) using nonlinear tunable sources

A series of experiments is described which were conducted to measure the absolute spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123–164 nm by two separate 1.0 μm lasers, i.e., using 100 Hz, 10 ns, 2–20 kHz, 60–100 ns full-width-at-half-maximum pulses. A maximum radiation conversion efficiency of ≈ 3%/2πsr is measured over a wavelength region from ≈ 125 to 160 nm. A developed collisional-radiative solver and radiation-hydrodynamics simulations in comparison to the spectra detected by the Seya–Namioka-type monochromator reveal the strong broadband experimental radiations which mainly originate from bound–bound transitions of low-ionized charges superimposed on a strong continuum from a dense plasma with an electron temperature of less than 10 eV.

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Plasma Parameters and Weakly Non-Ideal Behaviour of a High Density, Super-Atmospheric 2kA Cascade Arc in Argon

Zeitschrift für Naturforschung A ◽

10.1515/zna-1988-8-915 ◽

1988 ◽

Vol 43 (8-9) ◽

pp. 806-818 ◽

Cited By ~ 5

Author(s):

C. J. Timmermans ◽

G. M. W. Kroesen ◽

P. M. Vallinga ◽

D. C. Schram

Keyword(s):

Thermal Plasma ◽

Spectroscopic Studies ◽

Continuum Emission ◽

Plasma Parameters ◽

Ionization Degree ◽

Cascade Arc ◽

Far Ultraviolet ◽

Ideal Plasma ◽

A Current ◽

Ionized Systems

AbstractExperimental results are reported for simultaneous pressure and current pulses up to 14 bar and 2200 A superimposed on an atmospheric pressure 60 A dc cascade arc. A current density over 108 A/m2, previously 107 A/m2 (power density 1012W m3, previously 1010W/m3) has been obtained. The electron temperature of the thermal plasma was deduced from the end-on measured radiance of argon lines, and the electron density from the absolute continuum emission. The values found for the quantities mentioned during the quasi-stationary phase of the current pulse, lasting ~ 1 ms, were 27000 K and 3 · 1023 m-3, respectively, at a pressure of ~ 1.5 bar (ionization degree 100%), and 18000 K and > 1024 m-3, respectively, for a pressure of 14 bar (ionization degree 60%). These values satisfy the LTE relation. Deviations from the Spitzer conductivity have been observed in this weakly non-ideal plasma.In general, the high ionized thermal plasma studied with its composition of neutral, singly ionized and doubly ionized argon atoms can serve as a useful medium for spectroscopic studies of highly ionized systems and as a valuable source of radiation in the visible a well as in the near and far ultraviolet parts of the spectrum.

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Spectroscopic Studies on Unfolding Processes of Apo-Neuroglobin Induced by Guanidine Hydrochloride and Urea

BioMed Research International ◽

10.1155/2013/349542 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

Cui Zhang ◽

Chaohui Gao ◽

Jianshuai Mu ◽

Zhanglei Qiu ◽

Lianzhi Li

Keyword(s):

Structural Transition ◽

Guanidine Hydrochloride ◽

Fluorescence Emission ◽

Emission Spectra ◽

Spectroscopic Studies ◽

Native State ◽

Fluorescence Emission Spectra ◽

Unfolded State ◽

Partially Unfolded ◽

Far Ultraviolet

Neuroglobin (Ngb), a recently discovered globin, is predominantly expressed in the brain, retina, and other nerve tissues of vertebrates. The unfolding processes of apo-neuroglobin (apoNgb) induced by guanidine hydrochloride (GdnHCl) and urea were investigated by spectroscopic methods. In the unfolding processes, apoNgb's tertiary structural transition was monitored by the changes of intrinsic fluorescence emission spectra, and its secondary structural transition was measured by the changes of far-ultraviolet circular dichroism (CD) spectra. In addition, 8-anilino-1-naphthalenesulfonic acid (ANS), a hydrophobic cluster binding dye, was also used to monitor the unfolding process of apoNgb and to explore its intermediates. Results showed that GdnHCl-induced unfolding of apoNgb was via a three-state pathway, that is, Native state(N)→ Intermediate state(I)→ Unfolded state(U), during which the intermediate was inferred by an increase in fluorescence intensity and the change of CD value. Gibbs free energy changes are 10.2 kJ·mol−1for the first unfolding transition and 14.0 kJ·mol−1for the second transition. However, urea-induced unfolding of apoNgb only underwent a two-state transition: Native state(N)→ Partially unfolded state(P). The result showed that GdnHCl can efficiently affect the conformational states of apoNgb compared with those of urea. The work will benefit to have an understanding of the unfolding mechanism of apoNgb induced by GdnHCl and urea.

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