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  • 1
    Electronic Resource
    Electronic Resource
    Photoelectron spectra of and ab initio calculations on chlorobenzenes. 1. Chlorobenzene and dichlorobenzenes (1981)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 85 (1981), S. 1486-1489 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150611a007
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  • 2
    Electronic Resource
    Electronic Resource
    Photoelectron spectra of and ab initio calculations on chlorobenzenes. 2. Trichlorobenzenes, tetrachlorobenzenes, and pentachlorobenzene (1981)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 85 (1981), S. 1490-1495 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150611a008
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  • 3
    Electronic Resource
    Electronic Resource
    Photoelectron spectra of and ab initio calculations on chlorobenzenes. 3. Hexachlorobenzene (1981)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 85 (1981), S. 1495-1497 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150611a009
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  • 4
    Electronic Resource
    Electronic Resource
    On the heats of formation of trifluoromethyl radical CF3 and its cation CF3+ (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 210-221 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The CF+ and CF3+ fragment ion yield curves from C2F4 have been remeasured by photoionization mass spectrometry. Fits with appropriate model curves yield the appearance potentials AP0(CF3+C2F4)=13.721±0.005 eV and AP0(CF+/C2F4)=13.777±0.005 eV and an accurate difference in ionization potentials, IP(CF)−IP(CF3)=0.055±0.003 eV. With the existing photoelectron value IP(CF)=9.11±0.01 eV, this produces IP(CF3)=9.055±0.011 eV. The CF3+ fragments from CF3Cl, CF3Br, and CF3I have also been remeasured, and their ion yield curves fitted with model functions. The experimentally derived AP0(CF3+/CF3Cl)〈12.867±0.008 eV has been found to be only an upper limit. The Analogous CF33CF3+ fragment yield curves from CF3Br and CF3I produce AP0(CF3+/CF3Br)=12.095±0.005 eV and AP0(CF3+/CF3I)=11.384±0.005 eV, leading to D0(CF3−Br)=70.1±0.3 kcal/mol (70.8±0.3 kcal/mol at 298 K) and D0(CF3−I)=53.7±0.3 kcal/mol (54.3±0.3 kcal/mol at 298 K). Based on tabulated values for ΔHf&convolu;(CF3Br) and ΔHf&convolu;(CF3I), which appear to be inconsistent by ∼1 kcal/mol, a compromise value of ΔH298 f&convolu;(CF3)=−111.4±0.9 kcal/mol (−110.7±0.9 kcal/mol at 0 K) is selected, resulting in ΔH 298f&convolu;(CF3+)=97.4±0.9 kcal/mol (98.1±0.9 kcal/mol at 0 K). Additionally, IP(CF4)≡AP0(CF3+/CF4)=14.67±0.04 eV can be inferred. From data on C2F4, ΔH298f&convolu;(CF)=62.5±1.1 kcal/mol (61.7±1.1 kcal/mol at 0 K) can be deduced. Many earlier literature values for appearance potentials of CF3+ from CF3X, leading to very low ΔHf&convolu;(CF3+) and/or IP(CF3) values, are demonstrated to be in error. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473982
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  • 5
    Electronic Resource
    Electronic Resource
    On the heat of formation of carbonyl fluoride, CF2O (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9781-9795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In light of the recent controversy surrounding its heat of formation, CF2O was reexamined by photoionization mass spectrometry. In particular, the CO+ fragment ion yield curve from CF2O was interpreted in terms of a retarded CO++F2 process, and a more facile two-step fragmentation to CO++2F. The former process produces a weak, slowly growing tail region without a clear onset, while the latter occurs at higher energy and causes a pronounced growth with a conspicuous onset, which was found to occur at ≤20.87+0.03/−0.07 eV at 0 K by fitting with a model curve that incorporates "fluctuations'' associated with second-generation fragments. This onset leads to ΔHf° 298(CF2O) ≥−149.1+1.4/−0.7 kcal/mol, and indicates that the older experimental values for this quantity are too low by at least 3–4 kcal/mol. While the F2 elimination is retarded by competition with lower energy processes, the two-step process derives its strength from the FCO+ fragment, which assumes the role of a pseudoparent. Thus, the onset of CO++2F is expected to appear reasonably close to the thermochemical threshold. Such an interpretation indicates that recently calculated ab initio values of −145.3±1.7 kcal/mol and −145.6±1.0 kcal/mol are very likely too high by 3–4 kcal/mol. In addition, the adiabatic ionization potential of CF2O was refined to 13.024±0.004 eV, while the 0 K appearance potential of the FCO+ fragment was found by fitting to be ≤14.752±0.005 eV. Together with the suggested value for ΔHf°(CF2O), these two onsets lead to ΔHf° 298(CF2O+)=151.2+1.4/−0.7 kcal/mol and ΔHf° 298(FCO+)=173.5+1.4/−0.7 kcal/mol. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472848
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  • 6
    Electronic Resource
    Electronic Resource
    Direct observation of the ionization threshold of triplet methylene by photoionization mass spectrometry (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6748-6755 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoionization spectrum of the ionization threshold region of methylene has been recorded for the first time. The CH2 radical was produced in situ by successive hydrogen abstractions from methane precursor. The observed steplike onset corresponds to the vibrationless transition CH2+X˜ 2A1←CH2X˜ 3B1 and leads to the adiabatic ionization energy of CH2 of 10.393±0.011 eV. This value is slightly higher than the nominal midrise of the threshold step structure, which is depressed by rotational autoionization effects. In a separate set of experiments, the threshold region of the CH2+ fragment from CH3 was recorded at room temperature. The fragment appearance energy was accurately determined by fitting to be 15.120±0.006 eV at 0 K. The combination of these two measurements provides the best current experimental value for the bond dissociation energy of the methyl radical, D0(H–CH2)=4.727±0.012 eV=109.0±0.3 kcal/mol (corresponding to 110.4±0.3 kcal/mol at 298 K), and yields ΔHf0(minus sign in circle)(CH2,X˜ 3B1)=93.2±0.3 kcal/mol (93.3±0.3 kcal/mol at 298 K) and ΔHf0(minus sign in circle)(CH2,a˜ 1A2)=102.2±0.3 kcal/mol (102.3±0.3 kcal/mol at 298 K). The latter makes the reaction CH2 (a˜ 1A2)+H2O→CH3+OH essentially thermoneutral, ΔHr0(minus sign in circle)=0.0±0.3 kcal/mol. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476090
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  • 7
    Electronic Resource
    Electronic Resource
    Evidence of rotational autoionization in the threshold region of the photoionization spectrum of CH3 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9852-9856 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoionization spectrum of the threshold region of CH3 equilibrated at room temperature has been recorded and compared to the zero electron kinetic energy (ZEKE) spectrum of Blush et al. [J. Chem. Phys. 98, 3557 (1993)]. The ionization onset region is at ∼70 cm−1 higher energy than previous high-temperature photoionization work [Chupka and Lifshitz, J. Chem. Phys. 48, 1109 (1967)], but still ∼34 cm−1 lower than that implied by invoking only direct ionization. The residual discrepancy can be accounted for by including fully allowed quadrupole-induced and partially allowed dipole-induced rotational autoionization, thus making the observed onset completely congruous with the ZEKE ionization potential. In addition, the fragment appearance potential of CH3+ from CH4 was redetermined by accurate fitting as AP0(CH3+/CH4)=14.322±0.003 eV. With the very precise ZEKE ionization potential, this yields the best current value for the bond dissociation energy in methane, D0(H–CH3)=4.484±0.003 eV=103.40±0.07 kcal/mol (104.96±0.07 kcal/mol at 298 K). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475282
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  • 8
    Electronic Resource
    Electronic Resource
    A photoionization study of trifluoromethanol, CF3OH, trifluoromethyl hypofluorite, CF3OF, and trifluoromethyl hypochlorite, CF3OCl (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9111-9121 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: CF3OH, an important and controversial by-product of atmospheric decomposition of CF3CFH2 (HFC-134a) and other hydrofluorocarbons, has been examined by photoionization mass spectrometry. The ionization onset is characterized by a broad Franck–Condon distribution, arising primarily from a substantial elongation of the C–O bond upon ionization. An upper limit to the adiabatic ionization potential (IP) of ≤13.08±0.05 eV has been established. The appearance potentials (APs) of the first two fragments have been accurately determined by fitting with appropriate model functions as AP0(CF2OH+/CF3OH)≤13.830±0.005 eV and AP0(CF3+/CF3OH)≤13.996±0.005 eV. While the exact nature of the lowest-energy fragment (nominally CF2OH+) is not clear, the CF3+ fragment threshold leads unambiguously to ΔHf 298&convolu;(CF3OH)≥−217.2±0.9 kcal/mol and D298(CF3–OH)≤115.2±0.3 kcal/mol. With previously derived ΔHf 298&convolu;(CF3O)=−151.8−1.1+1.7 kcal/mol, this yields D298(CF3O–H)=117.5−1.4+1.9 kcal/mol, very close to, or only slightly weaker than the O–H bond energy in water: D298(CF3O–H)–D298(HO–H)=−1.8−1.4+1.9 kcal/mol(approximate)0 kcal/mol. Similarly, with the recently redetermined value for ΔHf&convolu;(CF2O), this implies a 298 K reaction enthalpy for the 1,2-elimination of HF from CF3OH of 2.8−1.1+1.7 kcal/mol. CF3OF and CF3OCl have also been examined by photoionization. CF3OF produces a very weak parent, with an apparent adiabatic IP(CF3OF)≤12.710±0.007 eV. An analysis of the CF3+ and CF2O+ fragments from CF3OF, when combined with literature data, suggests ΔHf 298&convolu;(CF3OF)=−176.9−1.3+1.8 kcal/mol. The fitted value for the appearance potential of CF3+ from CF3OCl, AP0(CF3+/CF3OCl)≤12.85±0.01 eV, leads to ΔHf 298&convolu;(CF3OCl)≥−175.6±1.0 kcal/mol, D298(CF3–OCl)≤88.4±0.3 kcal/mol, and D298(CF3O–Cl)≤52.8−1.5+2.0 kcal/mol.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474017
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  • 9
    Electronic Resource
    Electronic Resource
    Fourier transform photoelectron spectroscopy: The correlation function and the harmonic oscillator approximation (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 3776-3784 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The correlation function describes the time development of the wave packet placed by photoabsorption or photoionization onto the potential surface of an upper electronic state. The function can be obtained as a Fourier transform of the electronic band, and gives information about the features of the final state. The analytical expressions for the correlation function within the harmonic oscillator approximation are presented. Because of some unique properties of the correlation function, the expressions can be used to obtain accurate geometric details of the final state from experimental data. The approach is tested on some photoelectron spectra of diatomics and compared to known data. The method yields the equilibrium internuclear distance with an accuracy of ±0.0025 A(ring), and resolves the sign uncertainty present in the conventional harmonic Franck–Condon analysis. The comparison of the experimental data with the predictions of the harmonic model gives a deeper insight into the behavior of a wave packet in an anharmonic potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450898
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