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See detailDissociations between categorization and similarity judgements as a result of learning feature distributions
Thibaut, Jean-Pierre; Dupont, Myriam; Anselme, Patrick ULg

in Memory & Cognition (2002), 30(4), 647-656

A dissociation between categorization and similarity was found by Rips (1989). In one experiment, Rips found that a stimulus halfway between a pizza and a quarter was categorized as a pizza but was rated ... [more ▼]

A dissociation between categorization and similarity was found by Rips (1989). In one experiment, Rips found that a stimulus halfway between a pizza and a quarter was categorized as a pizza but was rated as more similar to a quarter. Smith and Sloman (1994) discussed these results in terms of the role of necessary and characteristic features. In two experiments, participants had to learn to categorize novel artificial shapes composed of a nonsalient necessary feature combined with a salient characteristic feature. Participants categorized stimuli on the basis of a necessary feature, whereas their similarity judgments relied on characteristic features. The role of deep (essential) features in dissociations is considered. Results are discussed in terms of the differences between requirements of categorization and similarity judgments. [less ▲]

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See detailDissociations between the processing of proper and common names
Brédart, Serge ULg; Brennen, T.; Valentine, T.

in Cognitive Neuropsychology (1997), 14(2), 209-217

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See detailDissociations between verbal short-term memory and phonological processing in Williams syndrome.
Majerus, Steve ULg; Barisnikov, K.; Poncelet, Martine ULg et al

Conference (2003, August)

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See detailDissociative Autoionization as a Mechanism for the Proton Formation from Methane and Methane-d4 by low energy Electron Impact.
Locht, Robert ULg; Olivier, J. L.; Momigny, J.

in Chemical Physics (1979), 43

The ion energy distribution and the electroionization efficiency curves of H+ and D+ from methane and methane-d4 have been examined. The existence of thermal ions is unambiguously evidenced and the two ... [more ▼]

The ion energy distribution and the electroionization efficiency curves of H+ and D+ from methane and methane-d4 have been examined. The existence of thermal ions is unambiguously evidenced and the two lowest appearance thresholds of H+ are measured at (21.3+/-0.3) eV and (22.17+/-0.1) eV. At both energies the protons have to be formed through dissociative autoionization. The present results closely parallel those of the dissociative excitation experiments on methane. The Jortner-Rice model for dissociation of polyatomic molecules is invoked to account for both the appearance of H+ and high-Rydberg H atoms from CH4. [less ▲]

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See detailThe Dissociative Electroionization of Ammonia and Ammonia-d3. I. The NH+ and NH2+ dissociation channels.
Locht, Robert ULg; Servais, Christian ULg; Ligot, M. et al

in Chemical Physics (1988), 123

The dissociative electroionization of NH3 (ND3) in the NH2+ (ND2+) and NH+(ND+) dissociation channels is investigated in the 15-50 eV electron energy range. The translational energy distributions of ND2 ... [more ▼]

The dissociative electroionization of NH3 (ND3) in the NH2+ (ND2+) and NH+(ND+) dissociation channels is investigated in the 15-50 eV electron energy range. The translational energy distributions of ND2+ (NH2+) exhibit several components whereas NH+ only shows a continuous broad distribution. For both ions a kinetic energy-versus-appearance energy diagram is obtained and discussed. The predissociation of the Jahn-Teller split NH3+(A2E) state produces both ions at their lowest threshold. At higher energies dissociative autoionization (in the 22 eV region), dissociative ionization through the NH3+(B2A1) state (in the 24-30 eV region) as well as by Coulomb repulsion of doubly ionized states (in the 35-50 eV region) produce NH2+(ND2+) and NH+ with large amounts of kinetic energy. Some arguments are brought forward to indicate that the former value of the NH2-H dissociation energy is overestimated. [less ▲]

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See detailThe Dissociative Electroionization of Ammonia and Ammonia-d3. II. The H+ and H2+ Dissociation Channels.
Locht, Robert ULg; Servais, Christian ULg; Ligot, M. et al

in Chemical Physics (1988), 125

The dissociative electroionization of NH3(ND3) in the H(D)+ and H(D)2+ dissociation channels is investigated in the 18-50 eV electron energy range. The H(D)+ translational energy distribution spectrum ... [more ▼]

The dissociative electroionization of NH3(ND3) in the H(D)+ and H(D)2+ dissociation channels is investigated in the 18-50 eV electron energy range. The H(D)+ translational energy distribution spectrum shows several components and that of H(D)2+ is continuous. The thermal energy component of the latter distribution is entirely ascribed to H2+/H2. For both ions the kinetic energy-versus-appearance energy diagram is obtained and discussed. The H+ ion at the lowest onset is probably formed at the expense of the NH3+(A2E) state. In the 22.5 eV electron energy range both H+ and H2+ are formed by dissociative autoionization. Evidence is also brought for H+ and H2+ formation at 22.5 eV and 26.5 eV through spontaneous decomposition of NH2+. Above 35 eV dissociation of doubly ionized states by Coulomb repulsion is mainly involved. [less ▲]

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See detailThe Dissociative Electroionization of Ammonia and Ammonia-d3. III. The N+ Dissociation Channel. General Conclusions about the Dissociation of NH3+.
Locht, Robert ULg; Momigny, J.

in Chemical Physics (1988), 127

The dissociative ionization of NH3 is investigated in its N+ dissociation channel in the 20-50 eV electron energy range. Both the translational energy distribution and the appearance energies are measured ... [more ▼]

The dissociative ionization of NH3 is investigated in its N+ dissociation channel in the 20-50 eV electron energy range. Both the translational energy distribution and the appearance energies are measured. The kinetic energy-versus-appearance energy plot reveals seven N+ producing processes. Near the onset (22.5-24.0 eV) dissociative autoionization occurs whereas direct dissociative ionization produces N+ in the 24.5-30 eV range. Above 35 eV mainly N+/H+ ion pairs are formed at the expense of doubly ionized states. The dissociative electroionization work on NH3 being completed a review of the results is presented. [less ▲]

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See detailThe Dissociative Electroionization of C2H2, C2D2 and C2HD. Investigation of the [C2H(D)]+ and [H(D)]+ Dissociation Channels. The (D)H-C2H(D) binding energy.
Davister, M.; Locht, Robert ULg

in Chemical Physics (1994), 189

The dissociative electroionization of C2H2 in the H+ and C2H+ dissociation channels has been extensively investigated in C2H2 and C2D2. The kinetic energy distributions and ionization efficiency curves of ... [more ▼]

The dissociative electroionization of C2H2 in the H+ and C2H+ dissociation channels has been extensively investigated in C2H2 and C2D2. The kinetic energy distributions and ionization efficiency curves of both species were examined in detail. The H(D)+ ion shows its lowest onset energy at 18.93+/-0.2 eV whereas the C2H+ is produced at 17.30+/-0.11 eV. For the H+-producing channel the kinetic energy (KE) versus the appearance energy (AE) diagram is obtained, extensively discussed and the bond dissociation energy D(H-C2H)= 5.33+/-0.23 eV is estimated. This value is compared and discussed with respect to the values found in the literature. Predissociation and dissociative autoionization are the dominant H+-producing mechanisms. At high electron energies doubly ionized states of C2H2 are involved. For C2H+, beside the threshold at 17.30+/0.11 eV a new onset at 18.27+/0.10 eV is observed. The ionization efficiency of the doubly ionized molecular ion is observed for the first time in C2HD isotopic species. [less ▲]

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See detailThe Dissociative Electroionization of Carbon Dioxide by low-energy Electron Impact. The C+, O+ and CO+ Dissociation channels.
Locht, Robert ULg; Davister, M.

in International Journal of Mass Spectrometry and Ion Processes (1995), 144

This work reports the dissociative ionization of CO2 between 19-40 eV. The three dissociation channels producing C+, O+ and CO+ are examined in detail. Translational energy distributions as a function of ... [more ▼]

This work reports the dissociative ionization of CO2 between 19-40 eV. The three dissociation channels producing C+, O+ and CO+ are examined in detail. Translational energy distributions as a function of the impinging electron energy and the ionization efficiency for fixed kinetic energy carried away by the fragments are measured. The kinetic energy versus appearance energy diagram is obtained for the three fragment ions. When available, the present results are compared with previous measurements. The lowest appearance energy of O+ and CO+ corresponds to the predissociation of the CO2+ (C2Sigma +/g) state. At higher energies all the fragment ions are exclusively produced by the dissociative ionization of CO2 in the multiple electron transition (MET) states. Predissociation is most probably the dominant mechanism. Each MET state branches off to produce not only the three fragments but also the same fragment in two different states. This is observed for each dissociation channel, i.e. O+, CO+ and/or C+. In the latter channel no evidence is found for the dissociative ionization reaction CO2+->C++2O. [less ▲]

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See detailThe Dissociative Electroionization of NH3 and ND3. A detailed Study of its five Dissociation Channels.
Locht, Robert ULg; Momigny, J.

in Longevialle, P. (Ed.) Advances in Mass Spectrometry. Volume 11A. (1988)

A general view of the results obtained for the dissociative ionization by electron impact on NH3 are presented. All five dissociation channels for the decomposition of the singly ionized NH3+ and the ... [more ▼]

A general view of the results obtained for the dissociative ionization by electron impact on NH3 are presented. All five dissociation channels for the decomposition of the singly ionized NH3+ and the doubly ionized (NH3)2+ are reported. [less ▲]

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See detailThe Dissociative Electroionization of NH3. The NH+ Dissociation Channel.
Locht, Robert ULg; Servais, Christian ULg; Ligot, M. et al

in Gilbody, H. B.; Newell, W. R.; Read, F. H. (Eds.) et al Electronic and Atomic Collisions: Abstracts of Contributed Papers. 15th International Conference on the Physics of Electronic and Atomic Collisions. Brighton, United Kingdom, 1987. (1987)

The dissociative electoionization efficiency of Nh3 in the NH+ channel is reported. The kinetic energy of this fragment ion is measured as a function of the impinging electron energy. Several dissociation ... [more ▼]

The dissociative electoionization efficiency of Nh3 in the NH+ channel is reported. The kinetic energy of this fragment ion is measured as a function of the impinging electron energy. Several dissociation limits are detected. [less ▲]

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See detailThe Dissociative Electroionization of Nitrous Oxide. The N+ and O+ Dissociation Channels.
Locht, Robert ULg; Olivier, J. L.; Momigny, J.

in Schmid, E. R. (Ed.) Book of Abstracts of the 9th International Mass Spectrometry Conference (1982)

The first results on the dissociative elctroionization of nitrous oxide in the N+ and O+ dissociation channels are reported in the 15-32 eV electron energy range. Dissociation mechanisms at several ... [more ▼]

The first results on the dissociative elctroionization of nitrous oxide in the N+ and O+ dissociation channels are reported in the 15-32 eV electron energy range. Dissociation mechanisms at several critical energies are presented. [less ▲]

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See detailThe Dissociative Electroionization of Nitrous Oxide. The O+ Dissociation Channel.
Olivier, J. L.; Locht, Robert ULg; Momigny, J.

in International Journal of Mass Spectrometry and Ion Physics (1983), 46

By electroionization mass spectrometry and ion kinetic energy analysis, the O+ fragment ion formation from N2O has been analyzed. Different appearance energies are measured and interpreted. Between the ... [more ▼]

By electroionization mass spectrometry and ion kinetic energy analysis, the O+ fragment ion formation from N2O has been analyzed. Different appearance energies are measured and interpreted. Between the onset at 15.27 eV and 22 eV only two dissociation limits are involved, i.e. O+(4S)+N2(X1Sigma+/g) at 15.29 eV and O+(2D)+N(X1Sigma+/g) at 18.61 eV. In both cases N2(X1Sigma+/g) is produced in its v=0 up to v=8 vibrational levels. Predissociation of ionic and Rydberg states of N2O are the dominant processes. [less ▲]

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See detailDissociative Electroionization Study in Acetylene. The Production of CH(D)+ in C2H2 and C2D2.
Davister, M.; Locht, Robert ULg

in Andersen, T.; Fastrup, B.; Folkmann, F. (Eds.) et al Electronic and Atomic Collisions: Abstract of contributed Papers. (1993)

An extensive study of the dissociative electroionization of C2H2(D2) in the CH(D)+ producing channel is reported. The translational energy-versus-appearance energy diagram reveals 9 CH+-producing ... [more ▼]

An extensive study of the dissociative electroionization of C2H2(D2) in the CH(D)+ producing channel is reported. The translational energy-versus-appearance energy diagram reveals 9 CH+-producing processes involving C2H2+ and (C2H2)2+ ionic states and is discussed in detail. [less ▲]

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See detailA Dissociative Electroionization Study of Nitrous Oxide. The NO+ and N2+ Dissociation Channels.
Olivier, J. L.; Locht, Robert ULg; Momigny, J.

in Chemical Physics (1982), 68

The decay of N2O into NO+ and N2+ dissociation channels has been investigated by electron impact using ions kinetic energy and mass analysis. The appearance energies of NO+ and N2+ are measured as a ... [more ▼]

The decay of N2O into NO+ and N2+ dissociation channels has been investigated by electron impact using ions kinetic energy and mass analysis. The appearance energies of NO+ and N2+ are measured as a function of the released translational energy. Both decay channels are mainly reached through predissociation of the N2O+ ionic states. In the NO+ decay channel, only one dissociation limit is involved, i.e. NO+(X1Sigma+,v)+N(4S) and hence the repulsive 4Sigma- state is responsible for all the observed phenomena. In the N2+ decay channel, several dissociation limits are involved. Dissociative ionization involving doubly excited states of N2O+ in both dissociation channels are briefly discussed. [less ▲]

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See detailA Dissociative Electroionization Study of Nitrous Oxide. The O+ and N+ Dissociation channels.
Olivier, J. L.; Locht, Robert ULg; Momigny, J.

in Chemical Physics (1984), 84

After the investigation of the decay of N2O into NO+ and N2+ the dissociation channels leading to O+ and N+ are examined by electroionization using ion kinetic energy and mass analysis. Appearance ... [more ▼]

After the investigation of the decay of N2O into NO+ and N2+ the dissociation channels leading to O+ and N+ are examined by electroionization using ion kinetic energy and mass analysis. Appearance energies of O+ and N+ are measured as a function of the kinetic energy of the fragment ions. Predissociation is the main mechanism for ion production in both channels. In the O+ decay channel the 4Sigma- state is an important intermediate. The neutral N2(X1Sigma+/g) mainly appears vibrationally excited. In the N+ dissociation channel, 2Pi states have to play an important role by predissociating the N2O(C2Sigma+) state and the higher-lying doubly excited states of N2O+. [less ▲]

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See detailDissociative Ionization by low energy Electron Impact. Energy Distribution and Appearance Energy of Doubly Ionized Fragments from N2 and O2.
Locht, Robert ULg; Momigny, J.

in Chemical Physics Letters (1979), 66(3), 574-577

Ion energy distributions and threshold energies are measured for the appearance of N2+ from N2. To our knowledge the same data are measured for the first time on O2+ from O2. For both ions a thermal peak ... [more ▼]

Ion energy distributions and threshold energies are measured for the appearance of N2+ from N2. To our knowledge the same data are measured for the first time on O2+ from O2. For both ions a thermal peak is observed in the ion energy distribution having an onset at (61.1+/-0.5) eV and (60.5+/-0.8) eV for the N2+ ion and the O2+ ion respectively. The appearance energy of higher energetic ions is measured and interpreted. [less ▲]

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See detailDissociative Ionization by low energy Electron Impact. Ion Energy Distribution of N++ from N2 and O++ from O2.
Locht, Robert ULg; Momigny, J.

in Electronic and Atomic Collisions: Abstracts of Contributed Papers. (1979)

The kinetic energy distribution of the doubly ionized species N++/N2 and O++/O2 , as produced by electron impact, is reported and discussed.

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See detailThe Dissociative Ionization in Oxygen.
Locht, Robert ULg; Schopman, Joop

in International Journal of Mass Spectrometry and Ion Physics (1974), 15

Dissociative ionization in O2 has been examined by means of a retarding potential lens combined with a quadrupole mass spectrometer. This particular arrangement made possible detailled analysis of the O ... [more ▼]

Dissociative ionization in O2 has been examined by means of a retarding potential lens combined with a quadrupole mass spectrometer. This particular arrangement made possible detailled analysis of the O+ ions kinetic energy distribution and the measurement of threshold energies of O+ ions with known kinetic energy. These two types of informations bring new experimental evidence, besides direct dissociative ionization of O2, for predissociation of the B2Sigma-/g state, the 2Piu state and the c4Sigma-/u state of O2+. A new predissociation of the O2+(2Deltag) state has been found. At low ion energy the predissociation of the 2Phiu state or an autoionizing predissociation is observed. [less ▲]

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