Quantum electronic control on chemical activation of methane by collision with spin-orbit state selected vanadium cation.

By coupling a newly developed quantum-electronic-state-selected supersonically cooled vanadium cation (V+) beam source with a double quadrupole-double octopole (DQDO) ion-molecule reaction apparatus, we have investigated detailed absolute integral cross sections (σ's) for the reactions, V+[a5DJ (J = 0, 2), a5FJ (J = 1, 2), and a3FJ (J = 2, 3)] + CH4, covering the center-of-mass collision energy range of Ecm = 0.1-10.0 eV.

Chemical Activation of Water Molecule by Collision with Spin-Orbit-State-Selected Vanadium Cation: Quantum-Electronic-State Control of Chemical Reactivity.

We have obtained absolute integral cross sections (σ's) for the reactions of spin-orbit-state-selected vanadium cations, V[aD( = 0, 2), aF( = 1, 2), and aF( = 2, 3)], with a water molecule (HO) in the center-of-mass collision energy range = 0.1-10.0 eV.

What is the Bond Dissociation Energy of the Vanadium Hydride Cation?

Recent electronic state-selected measurements of the reactions of atomic vanadium cations with D and CO are reanalyzed to properly account for the kinetic energy distribution of the reactant neutrals. The need for this is demonstrated in the present work by comparing the D data to that obtained previously in earlier experiments but unpublished. It is shown that the earlier data, which utilized a surface ionization source of V, and the state-selected data for V(D) are essentially identical in the threshold regions where they overlap.

Chemical Activation of a Deuterium Molecule by Collision with a Quantum Electronic State-Selected Vanadium Cation.

By combining a newly developed spin-orbit electronic state-selected ion source for vanadium cations (V) with a double quadrupole-double octopole mass spectrometer, we have investigated in detail the chemical reactivity or integral cross sections (σ's) for the reactions of V[aD ( = 0, 1), aF ( = 1, 2), and aF ( = 2, 3)] ion with a deuterium molecule (D). The vanadium deuteride ion (VD) is identified to be the only product ion formed in the center-of-mass collision energies of = 0.1-10.

Quantum state control on the chemical reactivity of a transition metal vanadium cation in carbon dioxide activation.

By combining a newly developed two-color laser pulsed field ionization-photoion (PFI-PI) source and a double-quadrupole-double-octopole (DQDO) mass spectrometer, we investigated the integral cross sections (σs) of the vanadium cation (V+) toward the activation of CO2 in the center-of-mass kinetic energy (Ecm) range from 0.1 to 10.0 eV.

Quantum Spin-Orbit Electronic State Selection of Atomic Transition Metal Vanadium Cation for Chemical Reactivity Studies.

By combining a pulsed laser ablation vanadium atom (V) beam source with the two-color laser sequential electric field pulse scheme for pulse field ionization-photoion (PFI-PI) detection, we have developed a quantum spin-orbit state selected transition metal ion source for ion-molecule reaction studies. As a demonstration, we show that the V ion can be prepared in the single spin-orbit levels of its three lowest quantum electronic states, V[aD ( J = 0-4), aF ( J = 1-5), and aF ( J = 2-4)], achieving laboratory kinetic energy ( E) resolutions of ≤0.2 eV.

Branching Ratios of the N(D) and N(D) Spin-Orbit States Produced in the State-Selected Photodissociation of N Determined Using Time-Sliced Velocity-Mapped-Imaging Photoionization Mass Spectrometry (TS-VMI-PI-MS).

Branching ratios for N(D) and N(D) produced by predissociation of state selected excited nitrogen molecules in the vacuum ultraviolet region have been measured for the first time. The quantum numbers of the excited nitrogen molecule are defined by selective excitation of the nitrogen molecule in the Franck-Condon region from the ground electronic, Σ, vibrational, v″, and rotational, J″ state to an excited E', v', J' state with a tunable vacuum ultraviolet, VUV, laser. The neutral atoms produced by predissociation from this excited state are then selectively ionized with a second tunable VUV laser.

Branching Ratio Measurements of the Predissociation of CO by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm.

Photodissociation of CO is a fundamental chemical mechanism for mass-independent oxygen isotope fractionation in the early Solar System. Branching ratios of photodissociation channels for individual bands quantitatively yield the trapping efficiencies of atomic oxygen resulting into oxides. We measured the branching ratios for the spin-forbidden and spin-allowed photodissociation channels of CO in the vacuum ultraviolet (VUV) photon energy region from 106 250 to 107 800 cm using the VUV laser time-slice velocity-map imaging photoion technique.

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion-Molecule Reaction of N(XΣ: ν = 0-2) + CH in the Collision Energy Range of 0.05-10.00 eV.

By implementing a vacuum ultraviolet laser-pulsed field ionization-photoion ion source with a double quadrupole-double octopole ion guide mass filter, we have obtained detailed quantum-vibrational-state-selected integral cross sections σ, ν = 0-2, for the ion-molecule reaction of N(XΣ: ν = 0-2) + CH in the center-of-mass kinetic energy range of E = 0.05-10.00 eV.

Quantum-state-selected integral cross sections for the charge transfer collision of O(aΠ: v = 1-2; J) [O(XΠ: v = 22-23; J)] + Ar at center-of-mass collision energies of 0.05-10.00 eV.

By employing the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully recorded the spin-orbit and rovibronic state resolved VUV-PFI-PI spectra for O(aΠ: ν = 0-2; J) and O(XΠ: ν = 21-23; J), indicating that O(aΠ) and O(XΠ) ions in these spin-orbit and rovibronic states can be prepared for ion-molecule collision studies. The present experiment is concerned with the measurement of absolute integral cross sections (σ's) of the charge transfer reactions, O(aΠ: ν = 1, 2; J) [O(XΠ: ν = 22, 23)] + Ar → Ar + O. The fact that the O(aΠ: ν = 1) and O(XΠ: ν = 22) [O(aΠ: ν = 2) and O(XΠ: ν = 23)] states are in close energy resonance, makes these reactions ideal model systems for investigating the energy resonance and Franck-Condon factor (FCF) effects on the charge transfer reactivity of O.

A quantum-rovibrational-state-selected study of the proton-transfer reaction H(XΣ: v = 1-3; N = 0-3) + Ne → NeH + H using the pulsed field ionization-photoion method: observation of the rotational effect near the reaction threshold.

Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H(XΣ: v = 1-3; N = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (ΔE ≈ 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational- as well as rotational-state effects on the proton transfer reaction of H(XΣ: v; N) + Ne.

A quantum-rovibrational-state-selected study of the reaction in the collision energy range of 0.05-10.00 eV: translational, rotational, and vibrational energy effects.

We report detailed absolute integral cross sections (σ's) for the quantum-rovibrational-state-selected ion-molecule reaction in the center-of-mass collision energy (E) range of 0.05-10.00 eV, where (vvv) = (000), (100), and (020), and .

A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH): determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH and CH.

We report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE) for the formation of methylium, CH, from methane, CH, as AE(CH/CH) = 14.32271 ± 0.

Isotopic and quantum-rovibrational-state effects for the ion-molecule reaction in the collision energy range of 0.03-10.00 eV.

We report detailed quantum-rovibrational-state-selected integral cross sections for the formation of HOvia H-transfer (σ) and HDOvia D-transfer (σ) from the reaction in the center-of-mass collision energy (E) range of 0.03-10.00 eV, where (vvv) = (000), (100), and (020) and .

High-Level ab Initio Predictions for the Ionization Energies, Bond Dissociation Energies, and Heats of Formation of Titanium Oxides and Their Cations (TiO/TiO, n = 1 and 2).

The ionization energies (IEs) of TiO and TiO and the 0 K bond dissociation energies (D) and the heats of formation at 0 K (ΔH°) and 298 K (ΔH°) for TiO/TiO and TiO/TiO are predicted by the wave-function-based CCSDTQ/CBS approach. The CCSDTQ/CBS calculations involve the approximation to the complete basis set (CBS) limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy (ZPVE), high-order correlation (HOC), core-valence (CV) electronic, spin-orbit (SO) coupling, and scalar relativistic (SR) effect corrections. The present calculations yield IE(TiO) = 6.

Comparison of experimental and theoretical quantum-state-selected integral cross-sections for the H2O(+) + H2 (D2) reactions in the collision energy range of 0.04-10.00 eV.

To understand the dynamics of H3O(+) formation, we report a combined experimental-theoretical study of the rovibrationally state-selected ion-molecule reactions H2O(+)(X(2)B1; v1(+)v2(+)v3(+); NKa(+)Kc(+)(+)) + H2 (D2) → H3O(+) (H2DO(+)) + H (D), where (v1(+)v2(+)v3(+)) = (000), (020), and (100) and NKa(+)Kc(+)(+) = 000, 111, and 211. Both quantum dynamics and quasi-classical trajectory calculations were carried out on an accurate full-dimensional ab initio global potential energy surface, which involves nine degrees of freedom. The theoretical results are in good agreement with experimental measurements of the initial state specific integral cross-sections for the formation of H3O(+) (H2DO(+)) and thus provide valuable insights into the surprising rotational enhancement and vibrational inhibition effects in these prototypical ion-molecule reactions that play a key role in the interstellar generation of OH and H2O species.

Rotationally Selected and Resolved State-to-State Photoelectron Study of Vanadium Monoxide Cation VO(+)(X(3)Σ(-); v(+) = 0-3).

Vanadium monoxide cation VO(+)(X(3)Σ(-)) has been investigated by two-color visible (VIS)-ultraviolet (UV) pulsed field ionization-photoelectron (PFI-PE) methods. The unambiguous rotational assignment of rotationally selected and resolved VIS-UV-PFI-PE spectra thus obtained confirms the ground state term symmetry of VO(+) to be X(3)Σ(-). The rotational analysis also yields the rotational constants Be(+) = 0.

State-to-state vacuum ultraviolet photodissociation study of CO2 on the formation of state-correlated CO(X(1)Σ(+); v) with O((1)D) and O((1)S) photoproducts at 11.95-12.22 eV.

The state-to-state photodissociation of CO2 is investigated in the VUV range of 11.94-12.20 eV by using two independently tunable vacuum ultraviolet (VUV) lasers and the time-sliced velocity-map-imaging-photoion (VMI-PI) method.

Rotationally resolved state-to-state photoionization and the photoelectron study of vanadium monocarbide and its cations (VC/VC(+)).

By employing two-color visible (VIS)-ultraviolet (UV) laser photoionization and pulsed field ionization-photoelectron (PFI-PE) techniques, we have obtained highly rotationally resolved photoelectron spectra for vanadium monocarbide cations (VC(+)). The state-to-state VIS-UV-PFI-PE spectra thus obtained allow unambiguous assignments for the photoionization rotational transitions, resulting in a highly precise value for the adiabatic ionization energy (IE) of vanadium monocarbide (VC), IE(VC) = 57512.0 ± 0.

Rotationally resolved state-to-state photoionization and photoelectron study of titanium carbide and its cation (TiC/TiC⁺).

Titanium carbide and its cation (TiC/TiC(+)) have been investigated by the two-color visible (VIS)-ultraviolet (UV) resonance-enhanced photoionization and pulsed field ionization-photoelectron (PFI-PE) methods. Two visible excitation bands for neutral TiC are observed at 16,446 and 16,930 cm(-1). Based on rotational analyses, these bands are assigned as the respective TiC((3)Π1) ← TiC(X(3)Σ(+)) and TiC((3)Σ(+)) ← TiC(X(3)Σ(+)) transition bands.

Photochemistry. Evidence for direct molecular oxygen production in CO₂ photodissociation.

Photodissociation of carbon dioxide (CO2) has long been assumed to proceed exclusively to carbon monoxide (CO) and oxygen atom (O) primary products. However, recent theoretical calculations suggested that an exit channel to produce C + O2 should also be energetically accessible. Here we report the direct experimental evidence for the C + O2 channel in CO2 photodissociation near the energetic threshold of the C((3)P) + O2(X(3)Σ(g)(-)) channel with a yield of 5 ± 2% using vacuum ultraviolet laser pump-probe spectroscopy and velocity-map imaging detection of the C((3)PJ) product between 101.

Rotationally resolved state-to-state photoelectron study of niobium carbide radical.

By employing the two-color visible (VIS)-ultraviolet (UV) laser photoexcitation scheme and the pulsed field ionization-photoelectron (PFI-PE) detection, we have obtained rovibronically selected and resolved photoelectron spectra for niobium carbide cation (NbC(+)). The fully rotationally resolved state-to-state VIS-UV-PFI-PE spectra thus obtained allow the unambiguous assignments of rotational photoionization transitions, indicating that the electronic configuration and term symmetry of NbC(+)(X̃) ground state are …10σ(2) 5π(4) 11σ(2) (X̃(1)Σ(+)). Furthermore, the rotational analysis of these spectra yields the ionization energy of NbC [IE(NbC)] to be 56,369.

Communication: direct measurements of nascent O((3)P0,1,2) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2) in VUV photodissociation of CO2.

We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2), formed by VUV photoexcitation of CO2 to the 4s(10 (1)) Rydberg state at 97,955.7 cm(-1).

Communication: State-to-state photoionization and photoelectron study of vanadium methylidyne radical (VCH).

By employing the infrared (IR)-ultraviolet (UV) laser excitation scheme, we have obtained rotationally selected and resolved pulsed field ionization-photoelectron (PFI-PE) spectra for vanadium methylidyne cation (VCH(+)). This study supports that the ground state electronic configuration for VCH(+) is …7σ(2)8σ(2)3π(4)9σ(1) (X(2)Σ(+)), and is different from that of …7σ(2)8σ(2)3π(4)1δ(1) (X(2)Δ) for the isoelectronic TiO(+) and VN(+) ions. This observation suggests that the addition of an H atom to vanadium carbide (VC) to form VCH has the effect of stabilizing the 9σ orbital relative to the 1δ orbital.