Ionization potentials, appearance potentials, and heats of formation of gaseous positive ions

Franklin, J. L.

doi:10.6028/nbs.nsrds.26

Cited by 280 publications

(100 citation statements)

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“…For the wavelength range covered here (10 eV-l1.8 eV), this is relatively simple in view of the fact that the parent ion is the only reactive primary ion in the system. The threshold for the formation of the vinyl ion, which is the major fragment ion observed in the 70 e V mass spectrum of the vinyl halides, is 12.5 e V and 12 e V for vinyl chloride and vinyl bromide respectively [ 4,16].…”

Section: Photolysis In the Photoionization Regionmentioning

confidence: 99%

Gas phase far ultraviolet photolysis and radiolysis of vinyl chloride

Ausloos

Rebbert

Wijnen

1973

J. RES. NATL. BUR. STAN. SECT. A.

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Quantum yi e lds of the major produ cts formed in the far ultravi ole t photolys is of CH,C DCI (C2 H2 , C, HD , C,HoD, C, H2 D" and 1,3·C, H,D,) have bee n de te rmin e d at 147 nm (8.4 e V), 123.6 nm (10.0 eV), a nd 104.8-106.7 nm 01.6-11.8 e V). The quantum yield of th e s tab le vinyl rad ica ls whi c h can be un· ambiguous ly asc ribed to the primary process (C H2CDCI + hll~ CH,C D+ CI) is 0.3 a nd 0.05 at 147 and 123.6 nm, res pe c tive ly. The sharp d ec rease in the yie ld of vinyl radicals with the in c re ase in e ne rgy of the in cid e nt photon beam is in part attribute d to the deco mposition of inte rnally e xcited vinyl radica ls to give acet yle ne as a produ c t. At 147 nm , th e co mbin ed yield of acet yle ne plu s vinyl rad icals is 0.95 ± 0.05. At the s horte r wa ve length s, approximate ly one acet yle ne molecul e is form ed per e lectronically excite d vinyl c hloride mol ec ule. It is conclude d that th e dissociative process: C2 HaCI* ~ C,H, + H + CI, occ urrin g via a C, Ha or C,H, CI inte rm e diate ade qu ate ly acco unts for the reo active ne utral s pecies form ed at higher photon e ne rgies. Isotopi c la belin g e xpe rim e nts s how that the hyd roge n atoms are d etac hed from both pos iti ons of th e pare nt molecule. Ethylene whic h is a produ ct over the e ntire wavel ength range is in part form e d via the reaction : H* + C,HaC I ~ C2H .. + CI, whe re H* re presents a translationa Uy e xcited hydrogen atom. The C2H2DC I+ ion s formed at 104.8 -106.7 nm with a quantum yie ld of 0.47 do not contribute to th e form ation of acetyle ne or vinyl radi c al s. In the gas phase radiolysis of vinyl c hlorid e, acetyl e ne (G -1. 5) is ma inly form e d in th e di ssocia tion of ne utra l e lectronica ll y excited vinyl c hlorid e molec ules. From this value, we may es tim ate th at the ratio of neutral excited molec ul es formation to ionization in th e rad iolys is of vinyl c hl orid e is 0.39. Vinyl ions, whi c h a re also prod uced (G -0.28-0.35) react ma inl y by addition to vi n yl c hlorid e.

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Section: Photolysis In the Photoionization Regionmentioning

confidence: 99%

Gas phase far ultraviolet photolysis and radiolysis of vinyl chloride

Ausloos

Rebbert

Wijnen

1973

J. RES. NATL. BUR. STAN. SECT. A.

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“…Synopses of the results have also been presented [3][4][5][6][8][9][10]14,17,18,[20][21][22][23][24][25][26][27][28]. Data obtained by this technique for individual compounds, whether gaseous or in the condensed phase, are incorporated in tabulations of dissociation energies [29][30][31][32][33][34][35][36][37][38], of thermodynamic properties [32][33][34][35][36][37][38], and of ionization potentials [30,39,40].…”

Section: Introductionmentioning

confidence: 99%

High-temperature mass spectrometry: Instrumental techniques, ionization cross-sections, pressure measurements, and thermodynamic data (IUPAC Technical Report)

Drowart

Chatillon

Hastie

et al. 2005

Pure and Applied Chemistry

227

184

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An assessment of high-temperature mass spectrometry and of sources of inaccuracy is made. Experimental, calculated, and estimated cross-sections for ionization of atoms and inorganic molecules typically present in high-temperature vapors are summarized. Experimental cross-sections determined for some 56 atoms are generally close to theoretically calculated values, especially when excitation–autoionization is taken into account. Absolute or relative cross-sections for formation of parent ions were measured for ca. 100 molecules. These include homonuclear diatomic and polyatomic molecules, oxides, chalcogenides, halides, and hydroxides. Additivity of atomic cross-sections supplemented by empirical corrections provides fair estimates of molecular cross-sections. Causes of uncertainty are differences in interatomic distances and in shapes of potential energy curves (surfaces) of neutral molecules and of molecular ions and tendency toward dissociative ionization in certain types of molecules. Various mass spectrometric procedures are described that render the accuracy of measured thermodynamic properties of materials largely independent of ionization cross-sections. This accuracy is comparable with that of other techniques applicable under the conditions of interest, but often only the mass spectrometric procedure is appropriate at high temperatures.

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“…[1][2][3][4] Although incomplete, they provide a large body of data on the heat of formation (∆ f H 0 ) of neutrals and ions and on ionization energies (IE). Most of the data are from experiment, but in cases where no experimental data are available, estimated values are sometimes reported.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Phenyl Substitution on the Thermochemistry of Gas-Phase Ions and Their Neutral Counterparts

Aubry

Holmes

2000

Eur J Mass Spectrom (Chichester)

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The available data for the heats of formation of phenyl-substituted organics have been critically evaluated. Phenyl substitution is always thermochemically destabilizing in thatis a positive quantity. The magnitude of the effect in neutrals depends on the substitution site, e.g. from + 79 kJ mol -1 for HCOR or HCCR to + 155 kJ mol -1 for RCO 2 H. Multiple phenyl substitution (where possible) at the same site is generally simply additive. For the corresponding cationic species, the first phenyl substitution is stabilizing when the ionization energy of the substrate is lowered thereby and for even-electron ions resonance-stabilization energies may also come into play. Additional phenyl substitution at the same site is, however, always destabilizing. Phenyl substitutions were compared with vinyl substitution: for neutral species the effects are similar, whereas for even-electron ions, multiple vinyl substitution is only weakly stabilizing or destabilizing.

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Ionization potentials, appearance potentials, and heats of formation of gaseous positive ions

Cited by 280 publications

References 0 publications

Gas phase far ultraviolet photolysis and radiolysis of vinyl chloride

Gas phase far ultraviolet photolysis and radiolysis of vinyl chloride

High-temperature mass spectrometry: Instrumental techniques, ionization cross-sections, pressure measurements, and thermodynamic data (IUPAC Technical Report)

The Effect of Phenyl Substitution on the Thermochemistry of Gas-Phase Ions and Their Neutral Counterparts

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