Observing the Maxwell–Boltzmann distribution in LED emission spectra

2010 ◽  
Vol 78 (9) ◽  
pp. 933-935 ◽  
Author(s):  
Jed Brody ◽  
Daniel Weiss ◽  
Pearl Young
Keyword(s):  
Emission Spectra ◽  
Boltzmann Distribution

Excited Species from a Pulsed Discharge in Helium at One Atmosphere Pressure

1995 ◽  
Vol 49 (9) ◽  
pp. 1282-1298 ◽  
Author(s):  
Wayne E. Wentworth ◽  
Yang Qin ◽  
Sophie Wiedeman ◽  
Stanley D. Stearns ◽  
Janardhan Madabushi
Keyword(s):  
Atmospheric Pressure ◽  
Emission Spectra ◽  
Atomic Emission ◽  
Boltzmann Distribution ◽  
Pulsed Discharge ◽  
Time Profiles ◽  
Direct Excitation ◽  
Excited Species ◽  
Radio Frequency Discharges ◽  
Atomic Helium

The relative intensities of atomic emission lines have been analyzed in regard to a Boltzmann distribution of the electronic levels in the pulsed discharge. The analysis confirms a Boltzmann distribution with an excitation temperature of 3200 ± 220 K, a relatively low temperature compared with that for other excitation sources, such as microwave and radio-frequency discharges. The analysis also suggests that little ionization occurs via direct excitation in the discharge. The emission spectra from excited diatomic helium states have been analyzed and confirm the formation of a32σu+) and the Hopfield emission He2( A1σu+ → 2He(11 S) continuum in the range 72 to 92 nm. Emission intensity-time profiles have been obtained for both atomic and diatomic helium emissions. Analysis of these profiles indicates that excited He2 states are obtained by two reactions: (1) an excited atomic helium reacting with a ground-state helium atom, and (2) recombination of He2+ with electrons. The study concludes that excitation in a discharge through helium at atmospheric pressure yields the following predominant species: He(23S), He2( a3σu+), Hopfield emission continuum 72–92 nm, and He2+.

Investigations into Trace Detection of Nitrocompounds by One- and Two-Color Laser Photofragmentation/Fragment Detection Spectrometry

2000 ◽  
Vol 54 (5) ◽  
pp. 651-658 ◽  
Author(s):  
Vaidhianat Swayambunathan ◽  
Rosario C. Sausa ◽  
Gurbax Singh
Keyword(s):  
Transition Probabilities ◽  
Pump Energy ◽  
Emission Spectra ◽  
Boltzmann Distribution ◽  
Integration Time ◽  
Distribution Analysis ◽  
Trace Detection ◽  
Analyte Molecule ◽  
Two Photon ◽  
Pump And Probe

Trace concentrations of nitrogen dioxide (NO2), nitromethane (CH3NO2), and 2,4,6-trinitrotoluene (TNT) are detected by both one- and two-color laser photofragmentation/fragment detection (PF/FD) spectrometry using one or two lasers. The PF/FD methods studied are (1) one-laser, one-color photofragmentation of the analyte molecule at 227 or 454 nm with subsequent detection of the characteristic nitric oxide (NO) photofragment by one- or two-photon laser-induced fluorescence using its A2Σ+ –X2π (0,0) transitions near 227 nm; (2) one-laser, two-color PF/FD, where a 355 nm laser beam is used for additional analyte photofragmentation and NO is detected by both one- and two-photon LIF as in the previous case; (3) two-laser, two-color PF/FD, where the pump and probe beams are time delayed; and (4) one-laser, one-color PF/FD at 355 nm, where the 355 nm beam photofragments the target molecule and the prompt emission from electronically excited NO (A2Σ+) is monitored in the range of 200–300 nm. PF/FD excitation and emission spectra are recorded and also simulated with the use of a computer program based on a Boltzmann distribution analysis with transition probabilities, rotational energies, and rovibrational temperatures as input parameters. The effects of laser wavelength, laser pump energy, time delay between pump and probe beams, and analyte concentration on PF/FD signal are investigated and reported. Limits of detection [signal-to-noise (S/N) = 3] for the nitrocompounds range from low ppbv to ppmv for 10 s integration time and laser energies of ∼ 5 mJ and 100 μJ for the pump and probe beams, respectively. These results are presented and compared to other PF/FD methods for nitrocompound monitoring.

Nano-probe x-ray analysis and high-resolution imaging on planar defects in high-pressure synthesized infinite-layer superconductor

1994 ◽  
Vol 52 ◽  
pp. 728-729
Author(s):  
Y. Y. Wang ◽  
H. Zhang ◽  
V. P. Dravid ◽  
H. Zhang ◽  
L. D. Marks ◽  
...  
Keyword(s):  
High Pressure ◽  
High Resolution ◽  
Atomic Structure ◽  
Emission Spectra ◽  
High Resolution Electron Microscopy ◽  
Planar Defects ◽  
X Ray ◽  
Infinite Layer ◽  
Resolution Electron ◽  
Resolution Imaging

Azuma et al. observed planar defects in a high pressure synthesized infinitelayer compound (i.e. ACuO2 (A=cation)), which exhibits superconductivity at ~110 K. It was proposed that the defects are cation deficient and that the superconductivity in this material is related to the planar defects. In this report, we present quantitative analysis of the planar defects utilizing nanometer probe xray microanalysis, high resolution electron microscopy, and image simulation to determine the chemical composition and atomic structure of the planar defects. We propose an atomic structure model for the planar defects.Infinite-layer samples with the nominal chemical formula, (Sr1-xCax)yCuO2 (x=0.3; y=0.9,1.0,1.1), were prepared using solid state synthesized low pressure forms of (Sr1-xCax)CuO2 with additions of CuO or (Sr1-xCax)2CuO3, followed by a high pressure treatment.Quantitative x-ray microanalysis, with a 1 nm probe, was performed using a cold field emission gun TEM (Hitachi HF-2000) equipped with an Oxford Pentafet thin-window x-ray detector. The probe was positioned on the planar defects, which has a 0.74 nm width, and x-ray emission spectra from the defects were compared with those obtained from vicinity regions.

Self-Consistent Field Calculations of X-Ray Emission Spectra of Surface Adsorbates and Polymers

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-515-C2-516
Author(s):  
H. Agren ◽  
L. G.M. Pettersson ◽  
V. Carravetta ◽  
Y. Luo ◽  
L. Yang ◽  
...  
Keyword(s):  
Emission Spectra ◽  
X Ray ◽  
Consistent Field ◽  
Self Consistent ◽  
Surface Adsorbates ◽  
Self Consistent Field

High resolution emission spectra of H2 and D2 near 80 nm

1980 ◽  
Vol 41 (12) ◽  
pp. 1431-1436 ◽  
Author(s):  
M. Larzillière ◽  
F. Launay ◽  
J.-Y. Roncin
Keyword(s):  
High Resolution ◽  
Emission Spectra

125Te MÖSSBAUER EMISSION SPECTRA OF TELLURIUM THIOUREA COMPLEXES

1979 ◽  
Vol 40 (C2) ◽  
pp. C2-417-C2-419
Author(s):  
C. H.W. Jones ◽  
M. Dombsky
Keyword(s):  
Emission Spectra

MÖSSBAUER EMISSION SPECTRA FROM57Co IN SIMPLE IONIC HALIDE CRYSTALS

1974 ◽  
Vol 35 (C6) ◽  
pp. C6-324-C6-324
Author(s):  
A. G. MADDOCK ◽  
A. F. WILLIAMS ◽  
J. FENGER ◽  
K. E. SIERKIERSKA
Keyword(s):  
Emission Spectra

EXPERIMENTAL AND THEORETICAL SOFT X-RAY EMISSION SPECTRA OF Cu-Pd SUBSTITUTIONAL ALLOYS

1987 ◽  
Vol 48 (C9) ◽  
pp. C9-1059-C9-1062
Author(s):  
P. J. DURHAM ◽  
C. F. HAGUE ◽  
J.-M. MARIOT ◽  
W. M. TEMMERMAN
Keyword(s):  
Emission Spectra ◽  
X Ray ◽  
Substitutional Alloys
Sign in / Sign up

Export Citation Format

Share Document