Coherent Vacuum Ultraviolet in Chemical Physics

Hepburn, J. W.

doi:10.1002/ijch.198400046

Cited by 26 publications

(5 citation statements)

References 60 publications

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“…Groundand excited-state Br have been monitored in a crossed beam experiment131 by excitation with coherent vacuum ultraviolet radiation produced by frequency mixing. 151 There has been considerable interest in the development of 2-photon excitation schemes for the detection of atoms in order to avoid the use of vacuum ultraviolet light. Most of the atoms on the right-hand side of the periodic table have now been detected by 2-photon A'n + 2s Figure 3.…”

Section: E Methods Applicable To Ionsmentioning

confidence: 99%

Spin-orbit effects in gas-phase chemical reactions

Dagdigian¹,

Campbell²

1987

Chem. Rev.

114

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Section: E Methods Applicable To Ionsmentioning

confidence: 99%

Spin-orbit effects in gas-phase chemical reactions

Dagdigian¹,

Campbell²

1987

Chem. Rev.

114

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“…The size of the VUV beam could not be measured directly, but from the size of the visible beams one can estimate that it was -4 mm in diameter in the middle of the photolysis cell. Absolute pulse energies were not measured, but the observed sensitivity for CO detection and the performance of other systems of nearly identical design 33 indicate that there were between lOll and 10 12 VUV photons in each 5 ns long pulse. The VUV light path was purged with argon to prevent attenuation by air.…”

Section: Methodsmentioning

confidence: 99%

Photofragmentation dynamics of formaldehyde: CO(v,J) distributions as a function of initial rovibronic state and isotopic substitution

Bamford

Filseth

Foltz

et al. 1985

The Journal of Chemical Physics

128

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Rovibronic state to rovibronic state reaction dynamics: O(3 P)+HCl(v=2,J)→OH(v′,N′)+Cl(2 P) Complete rotational distributions have been obtained for the CO produced following excitation of H 2 CO, HDCO, and D 2 CO near the S 1 origin. The CO was detected by vacuum ultraviolet laser-induced fluorescence. The distributions show a remarkable amount of rotational excitation, peaking at J = 42, 49, and 53 for H 2 CO, HDCO, and D 2 CO, respectively, with widths of 20-25 J units (FWHM). CO(v = 1) from H 2 CO photolysis has nearly the same rotational distribution as CO(v = 0). The population of CO(v = 1) is 14%±5% as large as the population of CO (v = 0), in good agreement with earlier measurements. Increased angular momentum of H CO is only partially transferred to CO, giving slightly wider rotational distributi~ns without changing the peak value. The rotational distributions are highly nonthermal, showing that energy randomization does not occur during the dissociation event. An approximate range of product impact parameters has been determined. The impact parameters are too large to be accounted for by forces along the directions of the C-H bonds. The hydrogen ~ppears to be most strongly repelled by the charge distribution a fraction of an A outside the carbon atom of the CO. The distribution of impact parameters and the internal energy of the hydrogen fragment apparently do not change significantly upon isotopic substitution. The absence of population in CO(J < 20) confirms the identity of CO(J > 25) as the long-lived intermediate in formaldehyde photodissociation.3032

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“…Diffusional processes are represented by the Warburg impedance (Z w ), which can be related to blockage of oxygen diffusion paths by corrosion products. [5][6][7] For a nondegraded polymer-coated metal system, before the interface becomes active, only the external circuit (R s , R f , C f ) will be observed experimentally. With time, however, the inner circuit (R ct , C dl , Z w ) may also become active, and this is the source of a second time constant.…”

Section: ͓2͔mentioning

confidence: 99%

The Correlation Between Substrate Mass Loss and Electrochemical Impedance Spectroscopy Data for a Polymer-Coated Metal

Mitton

Wallace

Cantini

et al. 2002

J. Electrochem. Soc.

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Research has been carried out to evaluate the correlation between substrate mass loss and data generated by electrochemical impedance spectroscopy ͑EIS͒. Experiments were carried out as a function of exposure time for both polymer-coated and bare samples. Mass loss was determined in situ and in real time with a vibrating sample magnetometer ͑VSM͒. In all cases, the sample was held potentiostatically at the open circuit potential ͑OCP͒ while EIS data were collected. Mass loss data calculated from electrochemical impedance ͑EI͒ spectra were then compared to equivalent data generated on the VSM. Although previous research has investigated the correlation for bare samples ͓W. J. Lorenz and F. Mansfeld, Corros. Sci., 21, 647 ͑1981͔͒ establishing this relationship for a coated substrate is more convoluted. The difficulty results from errors associated with solution uptake within the polymer, and corrosion product entrapment. Such errors obviate the use of traditional gravimetric techniques and, until now, the relationship between substrate mass loss and EIS has not unequivocally been established for polymer-coated samples. Although the current research indicates that EIS can accurately define the mass loss for a bare sample, the correlation for coated samples has, generally, not been as good.One methodology for reducing corrosion damage is painting or coating with an organic, and one of the most widely employed techniques for evaluating such polymer-coated systems is electrochemical impedance spectroscopy ͑EIS͒. Although the association between EIS data and mass loss for noncoated metals was previously described, 1 the analogous relationship for polymer-coated metals was not accurately defined prior to the current research. The difficulties in substrate mass loss determination are associated with solution uptake within a polymer, and corrosion product entrapment at the coating/metal interface. Such errors obviate the use of traditional gravimetric techniques. During the current study, the metallic mass loss for a polymer-coated metal was assessed and correlated to equivalent data produced by EIS. This was accomplished by utilizing a vibrating sample magnetometer ͑VSM͒ to magnetically quantify the mass loss for a polymer-coated cobalt substrate. These data were then correlated to corresponding mass loss data assessed by EIS.While degradation depends on a number of variables, 2 coatings isolate the substrate from direct contact with the environment and by retarding the arrival of reactants at the interface. Such coatings, however, tend to contain pores, defects, and virtual pores ͑Fig. 1͒, and, ultimately, underfilm corrosion is still likely to develop.When a material corrodes, it experiences a change in mass as a function of exposure time, and mass loss is, in many respects, the reference measurement against which all other techniques are assessed. During an electrochemical reaction, the proportionality between the current ͑I͒ and mass reacted ͑m͒ is defined by Faraday's lawwhere m is the change in mass, I is the curren...

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Coherent Vacuum Ultraviolet in Chemical Physics

Cited by 26 publications

References 60 publications

Spin-orbit effects in gas-phase chemical reactions

Spin-orbit effects in gas-phase chemical reactions

Photofragmentation dynamics of formaldehyde: CO(v,J) distributions as a function of initial rovibronic state and isotopic substitution

The Correlation Between Substrate Mass Loss and Electrochemical Impedance Spectroscopy Data for a Polymer-Coated Metal

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