Showing papers by "P. B. Armentrout published in 1999"
Abstract: Bond dissociation energies (BDEs) of M+[c-(C2H4O)5] and M+[c-(C2H4O)6] for M = Na, K, Rb, and Cs are reported. The BDEs are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation−crown ether complexes by xenon measured by using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissociation channel observed experimentally is endothermic loss of the ligand molecule. The cross section thresholds are interpreted to yield 0 and 298 K BDEs after accounting for the effects of multiple ion−molecule collisions, internal energy of the complexes, and unimolecular decay rates. For both 18-crown-6 and 15-crown-5, the BDEs decrease monotonically with increasing cation size. These results indicate that the intrinsic affinity of c-(C2H4O)5 and c-(C2H4O)6 for M+ is determined principally by the charge density of the cation not by the ratio of the ionic radius to the cavity size. The BDEs reported here are in fair agreement with recent ab initio...
186 citations
TL;DR: In this paper, the kinetic energy dependence of the V++CS2 reaction was examined using guided ion-beam mass spectrometry, where several different ion sources were used to systematically vary the V+ electronic state distributions and elucidate the reactivities of both the ground and excited state V+ cation.
Abstract: The kinetic-energy dependence of the V++CS2 reaction is examined using guided ion-beam mass spectrometry. Several different ion sources are used to systematically vary the V+ electronic state distributions and elucidate the reactivities of both the ground and excited state V+ cation. The cross section for VS+ formation from ground state V+(5D) exhibits two endothermic features corresponding to the formation of ground state VS+(3Σ−) and excited state VS+(5Π). The thresholds for these two processes are in good agreement with theoretically determined excitation energies. The cross section for spin-forbidden formation of ground state VS+(3Σ−) exhibits an unusual variation with kinetic energy that is attributed to the energy dependence of the surface-crossing probability. From the thresholds associated with the formation of VS+ and V(CS)+, D0(V+–S)=3.72±0.09 eV and D0(V+–CS)=1.70±0.08 eV are derived. Further, circumstantial evidence for formation of a high-energy isomer of V(CS)+ is obtained.
107 citations
TL;DR: In this paper, the bond energies of the metal-crown complexes have been analyzed by using a guided ion beam tandem mass spectrometer, and the experimental and theoretical results provided an extensive thermochemical database for evaluation.
100 citations
TL;DR: The kinetic method is examined from the point of view of a proponent of a complementary and sometimes competitive technique, threshold collision-induced dissociation as mentioned in this paper, and Limitations in the kinetic method and assumptions that have not been thoroughly examined in the literature are pointed out.
Abstract: The kinetic method is examined from the point of view of a proponent of a complementary and sometimes competitive technique, threshold collision-induced dissociation. Limitations in the kinetic method and assumptions that have not been thoroughly examined in the literature are pointed out. A case study involving recent experiments in the author's laboratory is used to illlustrate the importance of including entropic effects in the data analysis, even for systems where the ligands are fairly similar. The author concludes by encouraging the use of the advanced kinetic methods outlined by Cooks et al. in the accompanying Commentary. Copyright © 1999 by John Wiley & Sons, Ltd.
93 citations
TL;DR: In this article, the authors used a guided ion beam mass spectrometer to study the reactions of ground state Cu + (1 S, 3 D ) with O 2, CO, CO 2, N 2, NO, N 2 O, and NO 2.
82 citations
TL;DR: In this paper, collision-induced dissociation of M + (azole) with xenon was studied using guided ion beam mass spectrometry. And the cross-section thresholds were interpreted to yield 0 and 298 K bond energies for M + after accounting for the effects of multiple ion-molecule collisions, internal energy of the reactant ions, and dissociation lifetimes.
72 citations
TL;DR: In this paper, collision-induced dissociation of Na+−ROH with xenon was studied using guided ion beam mass spectrometry, and the cross section thresholds were interpreted to yield 0 and 298 K bond energies for Na++ROH after accounting for the effects of multiple ion−molecule collisions, internal energy of the reactant ions, and dissociation lifetimes.
Abstract: Collision-induced dissociation of Na+(ROH) with xenon is studied using guided ion beam mass spectrometry. ROH includes the following eight short chain alcohols: methanol, ethanol, 1-propanol, 2-propanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. In all cases, the primary product formed corresponds to endothermic loss of the neutral alcohol. The only other products that are observed in these reactions are the result of ligand exchange processes to form NaXe+. The cross section thresholds are interpreted to yield 0 and 298 K bond energies for Na+−ROH after accounting for the effects of multiple ion−molecule collisions, internal energy of the reactant ions, and dissociation lifetimes. Ab initio calculations at several levels of theory compare favorably to the experimentally determined bond energies. Trends in the Na+ binding energies are also compared to experimental values for the analogous Li+ systems.
66 citations
TL;DR: In this paper, the fundamental character of carbon dioxide activation at metal centers was studied in the gas phase using guided ion beam mass spectrometry, and the reactions of Y+ and YO+ with CO2 and the reverse reactions, YO+, YO2+, and O2Y(CO)+ with CO were investigated.
Abstract: Insight into the fundamental character of carbon dioxide activation at metal centers is studied in the gas phase using guided ion beam mass spectrometry. The reactions of Y+ and YO+ with CO2 and the reverse reactions, YO+ and YO2+ with CO, are investigated. To probe the potential energy surfaces of these systems more completely, YO2+ and the complexes OY(CO2)+, OY(CO)+, and O2Y(CO)+ are studied by collisional activation experiments with Xe. Thermochemical analysis of the reaction cross sections obtained in this study yield (in eV) D0(Y+−CO) = 0.31 ± 0.11, D0(OY+−CO) = 0.71 ± 0.04, D0(O2Y+−CO) = 0.69 ± 0.03, and D0(OY+−CO2) = 0.89 ± 0.05.
63 citations
TL;DR: The present results agree with previous experimental findings and also corroborate the computed data for FeS(+) and FeS (2)(+).
Abstract: Structural and thermochemical aspects of the FeS(2)(+) cation are examined by different mass spectrometric methods and ab initio calculations using density functional theory. Accurate threshold measurements provide thermochemical data for FeS(+), FeS(2)(+), and FeCS(+), i.e., D(0)(Fe(+)-S) = 3.06 +/- 0.06 eV, D(0)(SFe(+)-S) = 3.59 +/- 0.12 eV, D(0)(Fe(+)-S(2)) = 2.31 +/- 0.12 eV, and D(0)(Fe(+)-CS) = 2.40 +/- 0.12 eV. Fortunate circumstances allow a refinement of the data for FeS(+) by means of ion/molecule equilibria, and the resulting D(0)(Fe(+)-S) = 3.08 +/- 0.04 eV is among the most precisely known binding energies of transition-metal compounds. The present results agree with previous experimental findings and also corroborate the computed data for FeS(+) and FeS(2)(+). Ab initio calculations predict a sextet ground state ((6)A(1)) for FeS(2)(+) with a cyclic structure. The presence of S-S and Fe-S bonds accounts for the fact that not only reactions involving the disulfur unit but also sulfur-atom transfer can occur. In contrast, the FeS(2)(-) anion is an acyclic iron disulfide. In the gas phase, neutral FeS(2) may adopt either acyclic or cyclic structures, which are rather close in energy according to the calculations.
52 citations
TL;DR: Guided ion beam mass spectrometry was used to investigate the kinetic energy dependence of the reactions of Zr+ (4F) and ZrO+ (2Σ+) with CO2, and the reverse pathways, Zr O+ (1Σ+)-ZrO2+ with CO. as mentioned in this paper.
51 citations
TL;DR: In this paper, a spectroscopic study of the Rydberg states of YO accessed from particular rotational levels of the A 2 Π 1/2, v = 0 state has been combined with a pulsed field ionization, zero electron kinetic energy (PFI-ZEKE) investigation.
Abstract: A spectroscopic study of the Rydberg states of YO accessed from particular rotational levels of the A 2Π1/2, v=0 state has been combined with a pulsed field ionization, zero electron kinetic energy (PFI-ZEKE) investigation. The results provide accurate values of the ionization energy of YO, ionization energy I.E.(YO)=49 304.316(31) cm−1 [6.112 958(4) eV], and of the rotational constant (and bond length) of the YO+ cation in its X 1Σ+, v=0 ground state, B0+=0.4078(3) cm−1 [r0=1.7463(6) A]. The improved value of I.E.(YO) combined with the known ionization energy of atomic yttrium then leads to the result D00(Y−O)−D00(Y−O)=0.1041±0.0001 eV. Combining this result with the value of D00(Y+−O) obtained from guided ion beam mass spectrometry yields an improved value of D00(Y−O)=7.14±0.18 eV. The PFI-ZEKE spectra display an interesting channel-coupling effect so that all rotational levels with J+⩽J′(A)+0.5 are observed with high intensity, where J+ is the angular momentum of the YO+ cation that is produced and J′(...
TL;DR: In this article, the reactions of Ru + with C 2 H 6, C 3 H 8, HC(CH 3 ) 3, and c -C 3 H 6 at hyperthermal energies have been studied using guided ion beam mass spectrometry.
TL;DR: In this article, a review of the techniques associated with such studies are outlined with an emphasis on guided ion beam tandem mass spectrometry, and the use of this technique to measure thermodynamic information is highlighted.
Abstract: Studies of organometallic chemistry in the gas phase can provide substantial quantitative information regarding the interactions of transition metals with carbon centers. In this review, the techniques associated with such studies are outlined with an emphasis on guided ion beam tandem mass spectrometry. The use of this technique to measure thermodynamic information is highlighted. Periodic trends in covalent bonds between first, second and a few third row transition metals and small carbon ligands are discussed and shown to correlate with a carefully defined promotion energy. The bond energies for dative interactions between the first row transition metal ions and ethene, benzene and alkanes are also reviewed. With this thermochemical background, the reactions of atomic transition metal ions with alkanes (methane, ethane and propane) are reviewed and periodic variations in the reactivity are highlighted. An overview of our results on the effects of ancillary ligands (CO and H2O) and oxo ligands on the reactivity of transition metal centers are then provided.
TL;DR: In this paper, the reaction of FeS+ with D2 was examined by guided-ion beam mass spectrometry and three products, Fe+, FeD+, and FeSD+, were formed in endothermic processes, and thresholds for these reactions were dete...
Abstract: The reaction of FeS+ with D2 is examined by guided-ion beam mass spectrometry. Three products, Fe+, FeD+, and FeSD+, are formed in endothermic processes, and thresholds for these reactions are dete...