Paul Mack

The à 2Σ+ state of Ar⋅NO studied using resonance-enhanced multiphoton and zero-kinetic-energy pulsed-field ionization spectroscopy

Resonance-enhanced multiphoton ionization (REMPI) and zero-kinetic-energy pulsed-field ionization (ZEKE-PFI) techniques have been used to study the spectroscopy of the A 2Σ+ state of Ar⋅NO. A 2Σ+–X 2Π REMPI spectra of Ar⋅NO have been interpreted using two different models that have allowed assignment of the observed rovibronic transitions to be made and an estimate of the strength of the A state intermolecular potential to be determined. Simulations of the spectra have indicated that the ground vibrationless level of the A state has a linear geometry while some higher vibrational levels have a skewed T-shaped structure. The analysis has also confirmed that the A state of Ar⋅NO is very weakly bound and is non-Rydberg in character. Reported for the first time are ZEKE-PFI spectra observed via the intermediate A 2Σ+ state. No structure was detected close to the ionization threshold, although peaks observed at higher excitation energy have been assigned to transitions to high-lying vibrational levels of the ...

One‐ and two‐color resonance‐enhanced multiphoton ionization spectroscopy of the Kr⋅NO complex via the à 2Σ+ state

A structured spectrum of the A state of the Kr⋅NO complex has been obtained for the first time, employing the techniques of one‐color (1+1) and two‐color (1+1′) resonance‐enhanced multiphoton ionization spectroscopy. The T0 value of the A←X transition is 44 201±1 cm−1, and the spectrum allows estimates to be made of the dissociation energies (D0) of both the X and A states of ∼110 cm−1. Of significance is that the spectrum appears in both the Kr⋅NO+ mass channel and (when high photon intensities are used) in the Kr+ mass channel. Non‐Rydberg behavior of the A states of Ar⋅NO and Kr⋅NO is noted.

The C̃←X̃ transition in Ar⋅NO, Kr⋅NO, and Xe⋅NO studied using resonance-enhanced multiphoton ionization spectroscopy

The C 2Π(vNO′=0)←X 2Π(v″=0) transitions in Ar⋅NO and Kr⋅NO are investigated using (2+1) resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The spectra consist of vibrational progressions, each member of which is seen to have a reproducible pattern of much closer spaced features; the latter are assigned as rotational structure associated with the a inertial axis of a near T-shaped complex. The spectra are successfully simulated using this model, which yields information on the geometry of the molecular complex in these vibronic states. Comparison is made with previously reported spectra for the C 2Π(vNO′=1 and 2)←X 2Π(vNO″=0) transition. The corresponding spectrum for Xe⋅NO is also discussed.

Electronic and photoelectron spectroscopy of Rg·NO (Rg = rare as), NO·N2 and NO·CH4 molecular complexes

Abstract A critical review of experimental and ab initio studies of the Rg·NO complexes is presented. The review covers all the work published as of April 1998, and mainly concentrates on electronic [resonance-enhanced multiphoton ionization (REMPI), and laser-induced fluorescence (LIF)] spectroscopy, as well as photoelectron [zero-kinetic-energy (ZEKE)] spectroscopic studies. In addition, the NO·N 2 and NO·CH 4 molecule–molecule complexes are considered.

THE GEOMETRIC STRUCTURE AND STABILITY OF THE NO+ . CH4 CATIONIC COMPLEX

Abstract Ab initio calculationshave been performed, mainly at the MP2 level of theory, using a variety of basis sets, to elucidate the structure of the NO + ·CH 4 cationic complex. The complex has an equilibrium geometry of C s symmetry, in which the NO + moiety eclipses a CH bond of the methane molecule. The geometry is compared to those of related complexes. Harmonic vibrational frequencies are also calculated, together with the interaction energy and some thermodynamic quantities for the complex formation, employing a number of the theoretical methods. In particular, the interaction energy was calculated at the CCSD(T) level of theory. The implications of these results on the resonance-enhanced multiphoton ionization (REMPI) spectroscopy of the NO·CH 4 complex are briefly discussed.

Preliminary report of the observation of the à 2Σ+←X̃ 2Π transition in N2·NO

Abstract A structured spectrum of the A  2 Σ + ←X  2 Π transition of the N 2 ·NO complex has been recorded for the first time, employing the technique of one-colour (1+1) resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The T 0 value of the A  2 Σ + ←X  2 Π transition is determined as 44143.2±0.5 cm −1 and the dissociation energies of the X and A states are estimated as ∼88 and 144 cm −1 , respectively. The expected geometries and modes of bonding in the X and A states are discussed by comparison with those of similar complexes.

Ã←transition of Rg·NO complexes (Rg=rare gas) observed using resonance-enhanced multiphoton ionization (REMPI) spectroscopy Xe·NO

The A←transition of the Xe·NO molecular complex has been studied using one-colour (1+1) resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The spectrum shows a complicated vibrational structure, which terminates in a sharp cut-off. The spectrum was recorded in both the Xe·NO+ and the Xe+ mass channels; both spectra showed identical structure, except (i) the relative intensities of some of the features differed between the two spectra and (ii) Xe* transitions were observed in the Xe+ mass channel. The appearance of the Xe·NO spectrum in the Xe+ mass channel is discussed. The spectra allow the T0 value of the A←transition to be measured as 44163.2 cm-1 , as well as estimates to be made of the dissociation energy of both the and Astates: 121 and 157 cm-1, respectively. The vibrational structure observed in the spectrum was not analysed. No A←spectra of Ne·NO were observed under any of the conditions used. Trends in the spectroscopy and bonding of the Astate of the Rg·NO complexes (Rg=rare gas) are discussed, and the Astates of Ne·NO and He·NO are concluded to be either very weakly bound or dissociative.

Production of Rg+ ions in the resonance-enhanced multiphoton ionization spectroscopy of Rg · NO (Rg = Ar, Kr and Xe)

Abstract The observation of rare gas cations (Rg + ) in the multiphoton ionization of Rg · NO is studied. Kr + and Xe + are produced when exciting via the A state of Rg · NO, addition to Rg · NO + . In contrast, only Xe + is seen when exciting via the C state of Xe · NO, and only Kr · NO + is seen when exciting via the C state of Kr · NO. Ar + is not seen when exciting via either the A or C states of Ar · NO. The production of the different ions is studied as far of laser power by altering the laser intensity and focusing conditions. For excitation via the A state of Kr · NO, it is found that Kr + production is favoured by high laser intensities, with Kr · NO + being favoured by low intensities. Under tight focusing conditions for the one-colour experiments on Kr · NO, Kr + ions are also produced on NO A ← X resonances. Two-colour experimenrs are also performed on Kr · NO. The observation of Kr + on Kr · NO resonances is explained by intracomplex photoinduced charge transfer within the core of a Rydberg state, with collisional charge transfer between NO + and Kr · NO also playing a role. The production of Kr + on NO resonances is explained by photoinduced collisional charge transfer.