scholarly journals Zero- and Nonzero-Nuclear-Spin Isotope Response in Resonantly Enhanced Multiphoton Ionization of Kr nd Xe With Broad Band Lasers

1993 ◽  
Vol 13 (2) ◽  
pp. 159-165
Author(s):  
D. Charalambidis ◽  
Y. L. Shao ◽  
S. D. Moustaizis ◽  
C. Fotakis
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
Intermediate State ◽  
Broad Band ◽  
Multiphoton Ionization ◽  
Mass Analysis ◽  
Experimental Conditions ◽  
Broadband Laser ◽  
Photon Ionization ◽  
Ionization Response

The abundance of the 83Kr isotope, determined by ion mass analysis following three photon resonant four photon ionization via the 5s’ [1/2]1 state with a broadband laser is found to differ from the expected natural value. This effect is discussed in terms of a change of the ionization response due to the decay of coherence in the intermediate state to its hyperfine structure coupling. The nonzero nuclear spin isotopes of Xe have not shown any effect of this type in three different ionization schemes under the present experimental conditions.

scholarly journals Hyperfine structure in the arc spectrum of cæsium and nuclear rotation

1928 ◽  
Vol 121 (787) ◽  
pp. 432-447 ◽  
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
High Frequency ◽  
Principal Series ◽  
Very High Frequency ◽  
Nuclear Rotation ◽  
Higher Temperature ◽  
The Difference ◽  
Mechanical Moment ◽  
Very High

The arc spectrum of cæsium was investigated with the object of finding whether any of its lines possessed hyperfine structure, resulting from a nuclear magnetic moment, due to a quantised nuclear spin. The lines belonging to the principal series should, owing to the greater degree of penetration of the electron in the (1 s or 6 1 ) orbit, and the correspondingly greater interaction, show the greatest effect. The lines of the principal series are very easily broadened if the vapour pressure of the metal becomes high, so that great care had to be used in obtaining the spectrum of cæsium at a sufficiently low temperature. The most satisfactory method of excitation was found to be the application by means of external electrodes of a very high frequency alternating current to a tube filled with helium at about 2 mm. pressure containing a small quantity of cæsium. The tube required slight heating to bring out the cæsium lines; without this the helium spectrum was very much stronger than the metallic spectrum. At a very low vapour pressures of cæsium the discharge was blue in colour. Under these conditions the lines of the principal series showed no broadening greater than that due to thermal agitation, but at a slightly higher temperature the colour of the discharge became purple and the lines broadened. The lines belonging to the principal series were found to be very close doublets with very nearly constant frequencies differences. A theory is worked out which explains the origin of these doublets, assuming a nuclear spin of one half quantum; by correlating the difference in the separation of the hyperfine structure doublets in the 1 s — m 2 p 3/2 lines and the 1 s — m 2 p 1/2 lines, it is shown that a ratio of the magnetic to the mechanical moment of the nucleus about twice as great as the corresponding ratio for the electron would account for the observed frequency differences. The spectral notation used throughout is that of Hund. The results are compared with those found for the hyperfine structure of some of the bismuth lines by Back and Goudsmid, and are found to be in satisfactory agreement. A selection principle is found which applies both to the bismuth and the cæsium spectrum.

Nuclear Spin, Hyperfine Structure, and Nuclear Moments of 6.8-Day Lutetium-177

1962 ◽  
Vol 126 (1) ◽  
pp. 252-257 ◽  
Author(s):  
F. Russell Petersen ◽  
Howard A. Shugart
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
Nuclear Moments

Trace Detection of Nitrocompounds by ArF Laser Photofragmentation/Ionization Spectrometry

1993 ◽  
Vol 47 (11) ◽  
pp. 1907-1912 ◽  
Author(s):  
Josef B. Simeonsson ◽  
George W. Lemire ◽  
Rosario C. Sausa
Keyword(s):  
Ground State ◽  
Multiphoton Ionization ◽  
Ionization Mass ◽  
Trace Detection ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Detection Range ◽  
Arf Laser ◽  
Free Environment ◽  
193 Nm

A new method for detecting trace vapors of NO2-containing compounds near atmospheric conditions has been demonstrated with the use of one-color-laser photofragmentation/ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X2II electronic ground state and the other in its A2Σ+ excited state. Ionization of ground-state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via its A2Σ+ ← X2II (3, 0), B2II ← X2II (7, 0) and/or D2Σ+ ← X2II (0, 1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/ionization mass spectra.

OPTICAL FARADAY ROTATION STUDIES OF PARAMAGNETIC RESONANCE AND RELAXATION IN PRASEODYMIUM ETHYLSULPHATE

1965 ◽  
Vol 43 (12) ◽  
pp. 2361-2373 ◽  
Author(s):  
David J. Griffiths ◽  
Hans Glättli
Keyword(s):  
Hyperfine Structure ◽  
Liquid Helium ◽  
Faraday Rotation ◽  
Broad Band ◽  
Relaxation Times ◽  
Electron System ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Helium Bath ◽  
Half Power

The technique of detecting electron paramagnetic resonance and measuring paramagnetic relaxation times at liquid-helium temperatures by the magneto-optical Faraday rotation has been applied to the even number (4f2) electron system of Pr3+ in praseodymium ethylsulphate (PrES). The EPR spectrum (X band) of undiluted PrES at 1.37 °K is a broad band extending over several kilo-gauss with no evidence of hyperfine structure. The band intensity decreases at [Formula: see text] and covers [Formula: see text] from its maximum to half-power point. The absence of any hyperfine structure indicates that crystal-field distortion is the main source of line broadening.The relaxation times measured as a function of temperature over the range 1.40 to 2.18 °K and at 4.22 °K range from 0.1 to 10 msec. For [Formula: see text], τ decreases from 0.40 to 0.15 msec, is proportional to T−(3.5 ± 0.6), and is considered to be the phonon–bath relaxation time. Values of τ show a scatter within 0.20 ± 0.02 msec for [Formula: see text]. Near the λ point [Formula: see text], τ exhibits a very rapid increase, having a value of 0.20 msec at 2.155 °K and 0.85 msec at 2.165 °K. This behavior appears to be related to the energy exchange between the crystal and liquid-helium bath. Measurements of τ at 2.18 °K and 4.22 °K indicate that the rate at which the spin–phonon system returns to initial thermal equilibrium is governed by the thermal conductivity of the liquid-helium bath.

Detection of Atmospheric Pollutant NO With the Method of Resonant-Enhanced Multiphoton Ionization

2012 ◽  
Vol 209-211 ◽  
pp. 1596-1599
Author(s):  
Gui Yin Zhang ◽  
Yi Dong Jin ◽  
Hai Ming Zheng
Keyword(s):  
Decay Curve ◽  
Resonant State ◽  
Multiphoton Ionization ◽  
Photon Absorption ◽  
Ionization Cross ◽  
Atmospheric Pollutant ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photon Ionization ◽  
Key Substances

NO is one of the key substances of air pollution. This paper presents the use of the technique of resonant enhanced multi-photon ionization (REMPI) for NO ambient detection. NO is ionized by absorbing four photons and via A2Σ intermediate resonant state when use 452.4nm laser as radiation source. A physical model concerning the ionization process is presented. It is shown that the ion signal depends on laser character and the dynamic parameters of NO. Two-photon absorption and ionization cross section about the resonant state are obtained from the ion decay curve and the model. The detection limit of this work, which can reach 1.4 ppm, is determined by measuring the variation of the ion signal with the concentration of NO.

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