Infrared Predissociation Spectra Research Articles

Correction for Kemp et al. , The infrared predissociation spectrum of H 3 +

You have accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Kemp F., Kirk C. E. and McNab I. R. 2001Correction for Kemp et al., The infrared predissociation spectrum of H3+Phil. Trans. R. Soc. A.3592629http://doi.org/10.1098/rsta.2001.2000SectionYou have accessCorrection for Kemp et al., The infrared predissociation spectrum of H3+ F. Kemp F. Kemp Google Scholar Find this author on PubMed Search for more papers by this author , C. E. Kirk C. E. Kirk Google Scholar Find this author on PubMed Search for more papers by this author and I. R. McNab I. R. McNab Google Scholar Find this author on PubMed Search for more papers by this author F. Kemp F. Kemp Google Scholar Find this author on PubMed Search for more papers by this author , C. E. Kirk C. E. Kirk Google Scholar Find this author on PubMed Search for more papers by this author and I. R. McNab I. R. McNab Google Scholar Find this author on PubMed Search for more papers by this author Published:15 December 2001https://doi.org/10.1098/rsta.2001.2000This article corrects the followingResearch ArticleThe infrared predissociation spectrum of H3+https://doi.org/10.1098/rsta.2000.0656 E. Herbst, S. Miller, T. Oka, J. K.G. Watson, Faye Kemp, C. Euan Kirk and Iain R. McNab volume 358issue 1774Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences15 September 2000AbstractCorrection for ‘The infrared predissociation spectrum of H3+’ by F. Kemp, C. E. Kirk and I. R. McNab (Phil. Trans. R. Soc. Lond. A 358, 2403–2418. (doi: 10.1098/rsta.2000.0656)).On p. 2411 the statement ‘An important conclusion to be drawn from theory (Miller et al. 1989), which was largely verified, was that the intense lines in the clumps arose from transitions with small kinetic energy releases’ contains an incorrect reference. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsRelated articlesThe infrared predissociation spectrum of H3+15 September 2000Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences This Issue15 December 2001Volume 359Issue 1789Theme Issue ‘Non-smooth mechanics’ compiled by F. G. Pfeiffer Article InformationDOI:https://doi.org/10.1098/rsta.2001.2000Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online15/12/2001Published in print15/12/2001 License: Citations and impact

The infrared predissociation spectrum of H3+

Experimental measurements of the infrared predissociation spectrum of the H3+ ion are briefly reviewed. The spectrum involves states between -1100cm-1 and above +2000cm-1 of the dissociation limit ...

Infrared spectra of hydrogen-bonded ion–radical complexes: I−⋅HCH2 and Br−⋅HCHBr

We report the preparation and infrared spectra of the CH3I− and CH2Br2− anions formed by argon cluster-mediated electron attachment to the neutral molecular precursors. Infrared predissociation spectra were acquired for both the bare and argon-solvated species in the C–H stretching region. Partial rotational structure was recovered in the CH3I− system, consistent with the hydrogen-bonded, C2v structure suggested in an earlier analysis of its photoelectron spectrum [J. Kim et al., J. Am. Soc. Mass Spectrom. 10, 810 (1999)]. The spectrum and photofragmentation pattern confirm that this species is trapped in a very weakly bound ion–methyl radical form (I−⋅HCH2) involving a single ionic H bond. The CH2Br2− anion displays a similar spectrum, where one CH stretch is significantly redshifted, again signaling the single H-bonding motif.

Intermolecular interaction in the OH+–He and OH+–Ne open-shell ionic complexes: Infrared predissociation spectra of the ν1 and ν1+νb vibrations

Midinfrared spectra of the OH+–He/Ne open-shell ionic complexes have been recorded by photofragmentation spectroscopy in a tandem mass spectrometer. The ν1 vibration (OH stretch) and its combination band with the intermolecular bending vibration (ν1+νb) have been observed for both complexes at the level of rotational resolution. The analysis of the spectra shows that both complexes have a linear proton-bound structure in their 3Σ− electronic ground states, with intermolecular center-of-mass separations of 2.60 and 2.65 Å for OH+–He and OH+–Ne, respectively. The ν1 vibrational origins are redshifted by 66.3 and 169.9 cm−1 with respect to the corresponding monomer transition indicating that the intermolecular interaction increases upon ν1 excitation. The fine structure of the ν1 (3Σ−←3Σ−) and ν1+νb (3Π←3Σ−) transitions arising from electron spin and vibrational angular momentum of νb have been analyzed in terms of a semirigid Hamiltonian including spin–spin, spin–rotation, and l-type doubling interaction terms. The molecular parameters extracted from the molecular constants provide valuable information on the radial and angular part of the intermolecular potential-energy surface in each considered vibrational state. The intermolecular interaction in OH+–Ne is stronger than in OH+–He, mainly due to the larger polarizability of the rare-gas atom.

Infrared predissociation spectra of Nen–HN2+ clusters (n=1–5)

Infrared predissociation spectra of Nen–HN2+ (n=1–5) cluster ions have been recorded in the vicinity of the N–H stretching vibration (ν1) of HN2+. Several bands of the Ne–HN2+ dimer are rotationally resolved and provide direct information on the geometry, intermolecular stretching and bending frequencies, and complexation induced frequency shift of the ν1 vibration. The Ne–HN2+ complex has a linear, proton bound structure with an average separation between the Ne atom and the HN2+ center-of-mass of 〈1/R2〉−1/2=3.28 Å. The observed characteristics of the dimer are reproduced by a two-dimensional intermolecular potential energy surface calculated at the MP2 level, that is adiabatically corrected to account for the coupling of the intramolecular N–H stretching and intermolecular motions. The binding energy in the vibrational ground state of the complex is found to be 795 cm−1 and increases to 1005 cm−1 upon excitation of the N–H stretching vibration. Although the spectra of the larger complexes are not rotationally resolved, shifts in the ν1 transition frequency suggest that the larger clusters possess structures where the Ne atoms are weakly attached to the side of a linear Ne–HN2+ core.

Infrared predissociation spectra of He [sbnd]HO 2+ and Ne [sbnd]HO 2+: prediction of the gn1 frequency of HO 2+

Infrared spectra of theν 1 vibration (O H stretch) of the proton-bound He HO 2 + and Ne HO 2 + ionic complexes have been obtained by means of photodissociation spectroscopy in a tandem mass spectrometer. The measured vibrational frequencies of 2905 and 2761 cm −1 allow for an estimation of the unknownν 1 frequency of the HO 2 + monomer as3020 ± 40 cm −1.

Gateway states and bath states in the vibrational spectrum of H +3

Vibrational band intensities are obtained from discrete variable representation calculations of eigenstates for H + 3. Transitions linking highly excited states to the ground state show large variations in intensities, with gateway states corresponding to highly excited bending motion (“horseshoes”) which leak intensity into the nearby bath states. It is suggested that these gateway states may be observable. Implications of these results for the interpretation of the infrared predissociation spectra of H + 3 are discussed.

Infrared predissociation spectrum of the H3+ ion. II

The infrared predissociation spectrum of the H3+ ion has attracted considerable attention; theoretical models have been developed which account for many of the observed features and which make further predictions. This paper describes the results of experiments designed to test these predictions. The spectrum is recorded by bringing a mass-selected H3+ ion beam into parallel or antiparallel coincidence with a cw carbon dioxide infrared laser beam. In the earlier work, 27 000 lines were observed over the range 874–1094 cm−1, each line being recorded by detecting H+ fragment ions produced by predissociation. The spectrum varied according to the H+ kinetic energy window selected, and it was proved that many of the lines arise from metastable states of H3+ lying above the H2+H+ dissociation limit. The spectrum showed no immediately recognizable pattern, but low resolution convolutions revealed the existence of a coarse-grained structure of four main peaks. The isotopic species H2D+ and D2H+ showed similarly complex spectra which, however, differed depending on whether H+ or D+ fragments were detected. The most important conclusion from subsequent theoretical models is that the metastable states involved are in a region of classical chaos and hence cannot be simply assigned in terms of vibrational modes. However, the coarse-grained spectrum is associated with the remnants of a periodic orbit in which quasilinear H3+ undergoes a large amplitude bending motion. Rotational angular momentum barriers lead to trapping of these essentially regular states, which are embedded in a classically chaotic manifold. Semiclassical trajectory studies and three-dimensional quantum mechanical calculations are consistent with each other. Our present experimental methods are described and questions concerning reproducibility are addressed. We describe new measurements over the range 964–992 cm−1 spanning the position of one of the peaks observed earlier in the convoluted spectrum. The H3+ spectrum is recorded for a series of different H+ kinetic energy windows and the results are summarized in bar charts. Convolutions of the data recorded for H+ ions with very small center-of-mass kinetic energies are consistent with the earlier results and with theoretical predictions, but also reveal additional structure. Convolutions for large H+ kinetic energies (≥500 cm−1) reveal less evidence of characteristic structure. Measurements over the region 1025–1045 cm−1 are also described; they are only for very small H+ kinetic energy release, but the linewidths are also tabulated. Most of the metastable states of H3+ predissociate predominantly through a single channel, but examples of multiple dissociation channels have also been recorded. Direct measurements of some predissociation lifetimes are presented. Selected regions of the spectra of D2H+ and H2D+, measured by recording H+ and D+ fragments separately with kinetic energy windows from 0 to 3000 cm−1, are described. The results are in excellent agreement with theoretical predictions, as also are measurements of the background spontaneous predissociation.

Infrared spectrum of t-butyl hydroperoxide excited to the 4νOH vibrational overtone level

The infrared predissociation spectrum of t-butyl hydroperoxide excited to the 4νOH level reveals extensive mixing between the zeroth-order OH stretch state and nearly isoenergetic zeroth-order dark states. Because most of these dark states have an OH stretch quantum number of zero, the predissociation spectrum strongly resembles the infrared spectrum of an unexcited molecule. The observed intensity distribution in the predissociation spectrum is what one would expect if the eigenstates prepared by 4νOH vibrational overtone excitation were statistical mixtures of all the nearly isoenergetic zeroth-order states.

Local modes of HOOH probed by optical-infrared double resonance

We have used an optical-infrared double resonance technique to probe the nature of the eigenstates prepared by 4νOH vibrational overtone excitation in hydrogen peroxide. A visible dye laser excites the 4←0 OH stretch transition and an optical parametric oscillator promotes the molecules above the dissociation threshold by a ΔvOH=2 transition from the 4νOH level. Fixing the overtone excitation laser wavelength and scanning the wavelength of the infrared photon while monitoring the dissociation fragments by laser-induced fluorescence generates an infrared predissociation spectrum of the vibrationally excited molecule that contains information about vibrational state mixing at the 4νOH level. This spectrum indicates that the zeroth-order state that gives oscillator strength to the 4←0 OH stretch transition (i.e., the 4νOH bright state) is almost entirely comprised of a single vibrational eigenstate. Since the bright state is predominantly an OH stretch, the vibrational eigenstate prepared by 4νOH vibrational overtone excitation is well localized on the OH bond. This localization allows us to perform sequential local mode–local mode excitation of the two equivalent OH oscillators in HOOH.

Fine and hyperfine structure in thea 3II state of CH+

Spectroscopic and theoretical studies concerning thea 3II state of CH+ are reviewed, with particular consideration given to the infrared predissociation spectrum of the ion. This spectrum is primarily due to vibration-rotation transitions of thea 3II state involvingv=5 to 12 andJ=20 to 35. Some results of a spectral simulation, making use of a rotationally-adiabatic model, are presented to justify the proposed assignment. The nuclear-hyperfine structure of the observed transitions is studied in detail, with a new calculation of splittings presented. Some semi-quantitative conclusions can be drawn with reference to the variation of the Fermi Contact parameter,b, as a function of internuclear distance.

The infrared predissociation spectrum of triatomic hydrogen cation (H3+)

The purpose of this Account is to describe the remarkable infrared predissociation spectrum of H{sub 3}{sup +}. The H{sub 3}{sup +} molecular ion was first detected in 1911 by J.J. Thomson. It is an extremely stable species with a dissociation energy of 4.355 eV (420.236 kJ mol{sup {minus}1}) and is one of the main constituents of hydrogen plasmas, where its suppression is of some interest for prospects of nuclear fusion. As the simplest polyatomic molecule, H{sub 3}{sup +} has been the subject of many theoretical studies, which have been unanimous in their conclusion that its equilibrium geometry is that of an equilateral triangle.

High resolution infrared spectra of ethylene clusters

Infrared predissociation spectra have been measured for ethylene clusters near the ν7 (950 cm−1) monomer band using CO2 lasers. One of the CO2 lasers was piezoelectrically scanned over a 240 MHz range around each rotational lasing transition, to obtain high resolution spectra of the ν7 band. The resulting spectra showed fine structure with widths of the order of 20 MHz, representing a lower limit on the predissociation lifetime of around 10 ns. The fine structure is shown to be due to ethylene dimers, and the broad background is attributed to a superposition of inhomogeneous contributions from larger clusters.

High-resolution spectroscopy of ethylene clusters near 950 cm−1

Fine structure is observed in the infrared predissociation spectrum of ethylene dimer excited near the monomer v7 mode. The linewidths give a lower limit to the predissociation lifetime of 10 ns.

The infrared predissociation spectra of water clusters

Infrared predissociation spectra of water clusters have been measured in the frequency range 3000–3800 cm−1 using a molecular beam–color center laser apparatus. The transition from a spectrum resembling that of liquid water to that of the dimer is clearly seen. Detailed theoretical analyses using normal mode theory, local mode theory, and a quantum simulation method are used to interpret the spectrum in terms of a potential surface that includes both intramolecular and intermolecular degrees of freedom.

Sub-Doppler resolution infrared spectroscopy of the acetylene dimer: A direct measurement of the predissociation lifetime

Rotationally resolved, infrared predissociation spectra have been obtained for (C2H2)2 using a molecular beam apparatus in conjunction with a single mode F-center laser operating near 3300 cm−1. Several well separated bands are seen in the low resolution spectra, possibly indicating that more than one stable dimer structure exists. The high resolution spectra indicate that the widths of the individual rovibrational transitions, and hence predissociation lifetimes, depend on the band excited. The lifetimes obtained from the widths vary from 80×10−9 to 1.6×10−9 s.

Infrared predissociation spectra of water dimer in a supersonic molecular beam

The infrared absorption spectrum of the hydrogen-bonded water dimer, (H2O)2, formed in a supersonic expansion, was recorded in the region of th

Rotational structure in the infrared spectra of carbon dioxide and nitrous oxide dimers

High-resolution infrared predissociation spectra have been measured for dilute mixtures of CO 2 and N 2O in helium. Rotational fine structure is clearly resolved for both (CO 2) 2 and (N 2O) 2, the linewidths being instrument-limited. This establishes that predissociation lifetimes are longer than approximately 50 ns.