Resonance lamp

A iiseUfl light source is the helium resonance lamp which produces light of wavelength 58.4 nm or a photon energy of 21.2 eV, enough to ionize any neutral molecule. Often several peaks can be observed in the photoelectron spectnim... 

Our experimental techniques have been described extensively in earlier papers (2, 13). The gamma ray irradiations were carried out in a 50,000-curie source located at the bottom of a pool. The photoionization experiments were carried out by krypton and argon resonance lamps of high purity. The krypton resonance lamp was provided with a CaF2 window which transmits only the 1236 A. (10 e.v.) line while the radiation from the argon resonance lamp passed through a thin ( 0.3 mm.) LiF window. In the latter case, the resonance lines at 1067 and 1048 A. are transmitted. The intensity of 1048-A. line was about 75% of that of the 1067-A. line. The number of ions produced in both the radiolysis and photoionization experiments was determined by measuring the saturation current across two electrodes. In the radiolysis, the outer wall of a cylindrical stainless steel reaction vessel served as a cathode while a centrally located rod was used as anode. The photoionization apparatus was provided with two parallel plate nickel electrodes which were located at equal distances from the window of the resonance lamp. 

The standard astm test method (D-1149-64) for rubber damage includes a test chamber (volume, 0.11-0.14 m ) through which ozonized air flows at a rate greater than 0.6 m/s. Because the residence time of the ozonized air in the test chamber is about 1 s, the ozone may be expected to reach the material in about 0.1 s. A somewhat similar test procedure (aatcc test method 109-1972 ansi L14, 174-1973) is used in testing colorfastness. The ozone generator is usually (but not necessarily) a mercury-vapor resonance lamp with emission lines at 184.9 and 253.7 nm. The 184.9-nm line is absorbed, and two ground-state oxygen atoms are produced ... 

Gordon, R., Jr. Rebbert, R.E. Ausloos, P. Rare Gas Resonance Lamps. NBS Technical Note 496, 1969. 

Schuster54 reported that uridylic acid, Up, irradiated in buffered solution with a resonance lamp, formed the monohydrate which was identified by heat instability. If this material is warmed in alkaline solution, only 65% of the Up is recovered the other 35% decomposes to a new unidentified product (compound A) with the pyrimidine ring opened. Irradiation of the Up in frozen buffered solution produced the dimer, identified by photolytic reversion to Up. 

Smith32 reported that the absorbance of frozen cytosine solutions (0.5 mg/ml) decreased only 3-5% when irradiated with light from a mercury resonance lamp, but that the rate of loss of cytosine doubled when the frozen solution contained both cytosine and uracil. In solutions containing cytosine and thymine, a mixed dimer was apparently formed. Dried films of cytosine were apparently stable to the resonance radiation under conditions where there was 9% conversion of uracil and 17% conversion of thymine. There is a report that uracil dimer was formed in low yield in the photolysis of frozen cytosine solutions.32,81... 

Atomic absorption spectrometry (AA). This is a standard laboratory analytical tool for metals. The metal is extracted into a solution and then vaporized in a flame. A light beam with a wavelength absorbed by the metal of interest passes through the vaporized sample for example, to measure zinc, a zinc resonance lamp can be used so that the emission and absorbing wavelengths are perfectly matched. The absorption of the light by the sample is measured and Beer s law is applied to quantify the amount present. 

Chemical Conversion Methods. Laser-Induced and Resonance Fluorescence of HO. Considerable effort has been applied to the measurement of HO in the stratosphere and troposphere. Ultraviolet fluorescence techniques based on lasers or resonance lamps have received a great deal of attention and study. Because HO concentrations are typically factors of one-tenth to one-hundredth those of H02 in the atmosphere, the difficulties associated with making HO measurements by using fluorescence [low signal-to-noise ratio, laser-generated HO, background fluorescence, etc. see the... 

Tanaka and Steacie411 photolyzed NO using the 1236-A line of a krypton resonance lamp. They measured the current produced and found that it increased if krypton was added to the NO. They interpreted this as a krypton-photosensitized ionization, the krypton absorbing its own radiation more than the NO. 

Doppler and Pressure Broadening, 27 I 6.2 Line Profile in Resonance Emission Four Types of Resonance Lamps, 31... 

I 6.3 Measurement of the Absorplion Intensity Using a Resonance Lamp, 35... 

The steady state OH concentration in the atmosphere has been measured by the fluorescence technique using a dye laser tuned near 2820 A [Wang and Davis (1006), Davis ct al. (267)] or a microwave excited OH resonance lamp [Anderson (42)]. 

Resonance Lamp.—Such lamps (sometimes called low pressure lamps) are often used as line sources in photochemical studies. These usually contain a small amount of a metal vapor (e.g., mercury, cadmium, zinc, etc.) and several mm pressure of a rare gas. They operate at relatively low current (ca. 100 ma.) and high voltages (several thousand volts). This is in contrast to a typical medium pressure lamp which may operate off a 110-220 v. power supply delivering ca. 3-5 amp. The most common example in photochemistry is the mercury resonance lamp which has strong emission of the unreversed resonance lines at 2537 A. and 1849 A. (ca. 90% or more of the total) along with other, much weaker lines ( resonance lines are those which appear both in absorption and emission). There is little continuum. Sources of this type are widely used for photosensitized reactions. 

Further information on this system is available from studies directed at photochemical isotope enrichment (16). In this work a mercury resonance lamp containing only Hg19S was used as a source. A flowing mixture of natural mercury and water vapor exposed to the Hg198 fine structure component of the mercury resonance radiation (2537 A.) was found to result in HgO considerably enriched in Hg198. It was concluded that this could only occur if Hg(3Pj) atoms reacted in a primary step to form either a compound which is removed from further contact with the reaction or which itself may react further but must not regenerate free Hg. Either reaction (55) or (56) would satisfy these conditions. If reaction (55) is the primary reaction, the further reaction... 

During recent years real progress has been made in understanding a few of the reactions of excited mercury. If the primary step is (9) the reactions of the radicals will be the same in a given system no matter how they are formed. Mercury has seven stable isotopes and when ordinary mercury vapor is irradiated by a resonance lamp made of ordinary mercury all seven will be excited at rates proportional to their abundances and to the relative intensities of the hyperiine components from the resonance lamp. Even though some isotopes are more abundant than others and the intensities from the resonance lamp will be higher for the abundant isotopes than for others, there is no specificity about (9) and no dependence on isotopic composition would be expected. 

In some of the experimental work on this system a mercury resonance lamp made with isotope 202 has been used. Mercury with the usual isotopic distribution was mixed with the methyl chloride. Let X1 be the atomic fraction of isotope 202 in the HgCl formed and X1 be the atomic fraction of isotope 202 in ordinary mercury. Then... 

In spite of this very small range of absorption there is a preferential absorption by a single isotope when a mercury resonance line from a single isotope is used. The quantum yield of the isotopically specific step (50) with methyl chloride is 0.28 and of course part of the nonspecific step (49) will also be brought about by the isotope used to make the resonance lamp. 

Photoelectron spectroscopic studies were performed in an ultra-high-vacuum (UHV) photoelectron spectrometer, the details of which can be found elsewhere2 10. XPS was carried out using unfiltered Mg Ka radiation (125 3.6 eV photons), and with an electron energy analyser resolution such that the Au(4f7 2) line would have a FWHM of 0.9 eV. UPS was carried out with a He-resonance lamp, in connection with a 2 m grazing-incidence uv-monochromator, with the usual 21.2 eV and 40.8 eV photons. The electron energy analyser resolution was set to 0.2 eV in the XPS spectra and the Hell spectra, but to 0.1 eV in the Hel spectra. 

The Ar(3P(, Pt) levels are 11.623 and 11.827 eV, respectively, above the ground (1S) level. The lifetimes are 8.4 and 2.0 nsec (33), respectively. The Ar(3P,1 Pj) states are formed by absorption of the Ar resonance lines at 1067 and 1048 A. In the 1 to 100 mtorr concentration range the lifetime of Ar(3P, P() atoms is of the order of 10 /tsec [Hurst et al. (494)], which is 1000 times as long as that of isolated atoms because of imprisonment of resonance radiation. If the ionization potential ofa molecule is below 11.6 eV, it is possible to increase the photoionization yield (sensitize) by adding Ar to the sample. The increase of the ionization yield is caused by collisional energy transfer between Ar(3P, Pi) atoms and the molecule before the excited atoms return to the ground state by resonance emission. Yoshida and Tanaka (1065) have found such an increase in the Ar propane, and Ar-ammonia mixtures when they are excited by an Ar resonance lamp. Boxall et al. (123) have measured quenching rate constants for Ar(3P,) atoms by N2) 02, NO, CO, and H2. They are on the order of the gas kinetic collision rate. 

The present work involves measurement of k in a 0.1 atmosphere, stoichiometric CH -Air flame. All experiments were conducted using 3 inch diameter water-cooled sintered copper burners. Data obtained in our study include (a) temperature profiles obtained by coated miniature thermocouples calibrated by sodium line reversal, (b) NO and composition profiles obtained using molecular beam sampling mass spectrometry and microprobe sampling with chemiluminescent analysis and (c) OH profiles obtained by absorption spectroscopy using an OH resonance lamp. Several flame studies (4) have demonstrated the applicability of partial equilibrium in the post reaction zone of low pressure flames and therefore the (OH) profile can be used to obtain the (0) profile with high accuracy. 

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