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15 Dec 1984

Volume 81, Issue 12, pp. 5229-6413

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Internal field correction for infrared band intensity measured in solutions

Minoru Akiyama

J. Chem. Phys. 81, 5229 (1984); http://dx.doi.org/10.1063/1.447686 (2 pages) | Cited 8 times

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The Polo and Wilson equation has been widely used to eliminate the effect of the internal electric field from the observed infrared absorption intensities in the condensed phase. However, the validity of this equation for solution states has not been confirmed yet. This paper gives a new equation for the internal electric field correction in solution states according to the two kinds of molecular models. The equation obtained is identical to that of Polo and Wilson to the limit of pure liquid.
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33.20.Ea Infrared spectra
33.70.Fd Absolute and relative line and band intensities
78.30.C- Liquids
31.70.Dk Environmental and solvent effects

Orientational dynamics and disorder of solid adamantane as studied by infrared spectroscopy

Robert M. Corn, Victoria L. Shannon, Robert G. Snyder, and Herbert L. Strauss

J. Chem. Phys. 81, 5231 (1984); http://dx.doi.org/10.1063/1.447687 (8 pages) | Cited 10 times

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The CH stretching and bending vibrations of isotopically dilute C10D15H in a host crystal of perdeuterated adamantane have been monitored by infrared spectroscopy as a function of temperature from 7 to 300 K. The infrared bands depend upon both intramolecular and intermolecular interactions. The intramolecular splittings of the bands have been analyzed and compared with normal coordinate calculations. The intermolecular splittings of the CH stretches in the tetragonal phase are found to collapse and broaden with increasing temperature due to librational motion. A Redfield theory analysis of the temperature dependent line shifts and linewidths yields a correlation time of 2 ps for the adamantane libration. In the disordered plastic phase of adamantane, the intermolecular and intramolecular splittings of the CH stretches disappear and the rotational disorder yields a broad inhomogeneous band.
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63.50.-x Vibrational states in disordered systems
78.30.Jw Organic compounds, polymers

Diode laser detection of the bending mode of HCO+

P. B. Davies and W. J. Rothwell

J. Chem. Phys. 81, 5239 (1984); http://dx.doi.org/10.1063/1.447688 (2 pages) | Cited 26 times

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The infrared laser absorption spectrum of the bending fundamental of HCO+ has been detected using the velocity modulation technique. Assignment and measurement of 23 transitions yields a band center of 829.721(2) cm−1.
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33.20.Ea Infrared spectra

Theoretical study of the correlation and relativistic effects in the shakeup in the photoelectron spectrum of cesium

G. De Alti, P. Decleva, and A. Lisini

J. Chem. Phys. 81, 5241 (1984); http://dx.doi.org/10.1063/1.447689 (6 pages) | Cited 3 times

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Quasidegeneracy effects in the transitions in cesium are considered by relativistic and nonrelativistic CI calculations, and the interplay between correlation and relativistic effects is discussed. Dynamical correlation effects in the core shakeup are treated by nonrelativistic MCSCF calculations. Good agreement with experimental data is obtained and a revision of some features is suggested.
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32.80.Fb Photoionization of atoms and ions
31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions

Factor group splitting and dispersion on internal vibrational modes: A qualitative discussion

Ray Durman, Upali A. Jayasooriya, Sidney F. A. Kettle, Sudjit Mahasuverachai, Richard Mortimer, and Lars‐Johan Norrby

J. Chem. Phys. 81, 5247 (1984); http://dx.doi.org/10.1063/1.447690 (5 pages) | Cited 3 times

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Factor group splittings, of common occurrence in the infrared and Raman spectra of crystals, and dispersion, usually encountered in discussions of lattice modes, are shown to be closely related phenomena. Their relationship is elucidated by a model comprising a linear array of four vibrating units. A correlation between this and a similar two vibrator model indicates a method by which, in favorable cases, dispersion and mode change contributions to factor group splittings may be separately measured by conventional vibrational spectroscopies.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Hv Other nonmetallic inorganics
78.30.Jw Organic compounds, polymers

Visible and ultraviolet emission from pulse irradiated amorphous and polycrystalline H2O ice

C. G. Freeman, T. I. Quickenden, R. A. J. Litjens, and D. F. Sangster

J. Chem. Phys. 81, 5252 (1984); http://dx.doi.org/10.1063/1.447691 (3 pages) | Cited 5 times

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Luminescence peaking at 405 nm was observed when thin films of amorphous or polycrystalline ice at 97 K were irradiated with a pulsed beam of 0.53 MeV electrons. These emissions differed from the luminescence emitted by crystalline ice in that memory effects were not observed; the peak wavelengths were red shifted by ∼20 nm; and the half‐lives were 6–9 ns instead of ∼400 ns. The emission spectra of polycrystalline ice samples produced by rapid deposition or by annealing amorphous ice were similar, but both had substantially lower intensities than amorphous ice spectra.
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82.50.Hp Processes caused by visible and UV light
78.55.Hx Other solid inorganic materials

The three‐photon spectrum of the 1B2u←1A1g transition in benzene: Analysis of vibronic and rotational structure

S. G. Grubb, Charles E. Otis, K. S. Haber, and A. C. Albrecht

J. Chem. Phys. 81, 5255 (1984); http://dx.doi.org/10.1063/1.447692 (11 pages) | Cited 9 times

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A vibrational and rotational analysis of the three‐photon fluorescence excitation spectrum of the 1B2u←1A1g transition in gas‐phase benzene is presented. The group theoretically allowed origin and any associated vibrational structure are absent. In addition, there is no evidence for any rotational structure based on a rank‐three transition tensor. Coherent loss mechanisms are carefully considered and then rejected as possible interferences in the three‐photon fluorescence spectrum. Polarization measurements and observed vibronic structure indicate a dominant rank one (vibronic) contribution to the three‐photon cross section. The lack of three‐photon allowed structure in this 1B2u←1A1g transition of benzene is consistent with the pseudoparity selection rules of alternant hydrocarbon theory, yet such strict adherence to them would seem surprising. The appearance of the e2g mode ν8 in the three‐photon spectrum marks the first experimental determination of its frequency in the 1B2u state.
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33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.80.Wz Other multiphoton processes
33.20.Lg Ultraviolet spectra
33.20.Vq Vibration-rotation analysis

19F nuclear magnetic shielding scale from gas phase studies. II

Cynthia J. Jameson, A. Keith Jameson, and Jila Honarbakhsh

J. Chem. Phys. 81, 5266 (1984); http://dx.doi.org/10.1063/1.447693 (2 pages) | Cited 16 times

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The absolute 19F nuclear magnetic shielding at 300 K is reported for 13 molecules containing 21 chemically different 19F nuclei.
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33.25.+k Nuclear resonance and relaxation

Orientational ordering and site structure of SiF4 trapped in rare gas solids

Llewellyn H. Jones, Basil I. Swanson, and Scott A. Ekberg

J. Chem. Phys. 81, 5268 (1984); http://dx.doi.org/10.1063/1.447667 (4 pages) | Cited 8 times

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The infrared spectrum of the ν3 mode of SiF4 shows only one site with marked site‐symmetry splitting accompanied by pronounced (>95%) orientational ordering. The results indicate a site symmetry of C3v with the SiF4 molecule occupying a four‐atom substitutional site with a cubic‐close‐packed environment. In krypton and xenon matrices, however, SiF4 occupies a three‐atom substitutional site. The fact that SiF4 shows only one dominant site when present in argon matrices of UF6 indicates that one of the two UF6 sites has a local hexagonal close packed environment induced by short range stacking faults.
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33.20.Ea Infrared spectra

Determination of ESR inhomogeneous line broadening for nitroxide radicals arising from heterogeneous environments of amorphous substances

Sook Lee, D. P. Ames, and I. M. Brown

J. Chem. Phys. 81, 5272 (1984); http://dx.doi.org/10.1063/1.447668 (3 pages) | Cited 6 times

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It has recently been shown that the ‘‘single‐crystal’’ linewidths of anisotropic magnetic resonance centers in amorphous or polycrystalline samples can be measured with high accuracy by means of second‐derivative powder spectra. Based on this second‐derivative‐powder‐spectrum method, a new approach is presented for reliably determining the inhomogeneous electron‐spin‐resonance (ESR) line broadening of nitroxide radicals arising from heterogeneous environments of amorphous substances. The experimentally measured values of this inhomogeneous line broadening can be employed for characterizing structural deviations of nitroxide spin labels and probes due to heterogeneous environments of nitroxide host matrices.
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76.30.Rn Free radicals
33.35.+r Electron resonance and relaxation
33.70.Jg Line and band widths, shapes, and shifts

Proton magnetic resonance study of the H2–He potential energy surface

Claude Lemaire, Robin L. Armstrong, and Frederick R. McCourt

J. Chem. Phys. 81, 5275 (1984); http://dx.doi.org/10.1063/1.447669 (6 pages) | Cited 16 times

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Measurements of the proton spin‐lattice relaxation time (T1) carried out at 18.775 MHz in two H2–He mixtures are presented. Values of T1/ρ)∞lin, accurate to within 2%, are deduced for ten temperatures between 85 and 300 K. These data are compared with theoretical values deduced from various H2–He potential surfaces. It is shown that the data are quite capable of distinguishing between the various surfaces and that the most recent H2–He surface of Kohler and Schaefer gives an excellent representation of the data.
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33.25.+k Nuclear resonance and relaxation
36.40.-c Atomic and molecular clusters

A study of the ν1 fundamental and bend‐excited hot band of DNN+ by velocity modulation absorption spectroscopy with an infrared difference frequency laser

David J. Nesbitt, Hrvoje Petek, Christopher S. Gudeman, C. Bradley Moore, and Richard J. Saykally

J. Chem. Phys. 81, 5281 (1984); http://dx.doi.org/10.1063/1.447670 (7 pages) | Cited 20 times

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The combined application of the ac discharge velocity modulation technique with cw tunable difference frequency infrared generation and dual beam subtraction of laser amplitude noise produces an extremely sensitive (10−6 absorbance/Hz1/2) direct absorption method for observing vibrational spectra of molecular ions. In this study we report observation of the fundamental ν1 (D–N stretch) of DNN+ in both P and R branches from J=0 to 24, as well as the 30‐fold weaker hot band transitions originating from the (0110) bending state. l‐doubling in these latter transitions is measured interferometrically with a precision of ±10 MHz. Spectroscopic constants for (0000), (1000), (0110), and (1110) states are reported and compared with ab initio calculations and previous microwave measurements for DNN+.
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33.20.Ea Infrared spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
98.38.Bn Atomic, molecular, chemical, and grain processes
98.38.Er Interstellar masers
98.58.Bz Atomic, molecular, chemical, and grain processes
98.58.Ec Interstellar masers

Model based calculations of the lattice mode spectra of ice Ih and amorphous solid water

Glen Nielson, R. Michael Townsend, and Stuart A. Rice

J. Chem. Phys. 81, 5288 (1984); http://dx.doi.org/10.1063/1.447671 (14 pages) | Cited 17 times

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We report calculations of the translational and librational mode regions of the Raman and infrared spectra of ice Ih and amorphous solid water. The models used for these materials are those proposed by Bergren and Rice [J. Chem. Phys. 77, 583 (1982)] and Madden et al. [J. Chem. Phys. 69, 3497 (1978)]. There is good agreement between the calculated and observed librational mode spectra. The disagreement between the calculated and observed translational mode Raman and infrared spectra, together with agreement between calculated and observed translational mode densities of states, supports the suggestion by Klug and Whalley [J. Glaciology 21, 551 (1978)] that electric field induced mixing of translational states is important in ice Ih.
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78.30.Hv Other nonmetallic inorganics
61.43.Fs Glasses
61.43.-j Disordered solids

Torsional potential and intramolecular dynamics in the C2H+4 photoelectron spectra

J. E. Pollard, D. J. Trevor, J. E. Reutt, Yuan T. Lee, and D. A. Shirley

J. Chem. Phys. 81, 5302 (1984); http://dx.doi.org/10.1063/1.447672 (8 pages) | Cited 28 times

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The 584 Å photoelectron spectrum of ethylene was reexamined at higher resolution using a supersonic molecular beam source for rotational cooling. The vibrational frequencies of the C2H+4math 2B3 state were measured with improved accuracy, which permitted the torsional potential energy curve to be characterized. The measured equilibrium torsional angle is 27°∗2°, and the inversion barrier is 270±150 cm−1. The math 2B3 state is shown to be in reasonable agreement with a recent theoretical calculation which takes into account strong nonadiabatic effects. The correlation function calculated for this state is consistent with this calculation and recent calculations on the unimolecular dissociation of this state. The math 2A state correlation function indicates a rapid decay mechanism is operative. The broadened vibrational structure in the fourth band results from a saddle point in the math 2B2 potential energy surface from which the ion relaxes to the math state by moving along a repulsive degree of freedom, which in this case is internal rotation. The math state vibrational broadening as well as the decay of the correlation function yield a lifetime for this process of 7 fs.
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33.60.+q Photoelectron spectra
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

Optical dephasing and photon echoes from energetically and substitutionally disordered crystals

L. Root and J. L. Skinner

J. Chem. Phys. 81, 5310 (1984); http://dx.doi.org/10.1063/1.447673 (9 pages) | Cited 28 times

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For a crystal with both diagonal disorder (inhomogeneous broadening) and substitutional disorder we have calculated the contribution to the photon echo decay due to purely electronic intersite interactions. We have considered the two important limiting cases of macroscopic and microscopic inhomogeneous broadening. In the case of macroscopic broadening we find that the optical dephasing rate constant 1/T2∼f J, where  f is the fractional concentration of impurities and J is the nearest‐neighbor intersite interaction in frequency units. This result is valid for  f≪1. In the opposite limit of microscopic inhomogeneous broadening, we find that 1/T2∼f J2/δ, where δ is the width in frequency units of the inhomogeneous distribution. This result is valid for arbitrary  f, including  f=1, and for J≪δ. In the case that  f≪1 and J≪δ, 1/T2 is much smaller for microscopic broadening than for macroscopic broadening. We discuss our results in relation to several experiments on mixed molecular crystals and to an experiment on the stoichiometric material EuP5O14.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
71.55.Jv Disordered structures; amorphous and glassy solids

The high‐resolution visible overtone spectrum of CH4 and CD3H at 77 K

G. J. Scherer, Kevin K. Lehmann, and W. Klemperer

J. Chem. Phys. 81, 5319 (1984); http://dx.doi.org/10.1063/1.447674 (7 pages) | Cited 57 times

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We have obtained visible overtone spectra with Doppler‐limited resolution of methane and trideuteromethane in the vicinity of six quanta of C–H stretch. At room temperature, the methane spectrum is unresolved. Upon cooling to 77 K in a specially designed photoacoustic cell, methane shows a complicated but rotationally resolved spectrum. The widths of all features in the spectrum are consistent with Doppler broadened linewidths at 77 K. Efforts to assign this spectrum are in progress. The overtone spectrum of CD3H has been recently studied by other workers at a resolution of 0.5 cm−1 [Perry, Moll, Kupperman, and Zewail (preprint)]. The spectrum in this region consists of two parallel bands, one at 16 156 cm−1 and another at 16 230 cm−1. These are assigned as arising from a Fermi resonance between the pure C–H overtone 6ν1 and a combination with the degenerate C–H bend, 5ν1+2ν5. A high resolution spectrum taken at 77 K shows nearly completely resolved K‐subband structure for both bands. The rotational constants of both states cannot be rationalized purely on the basis of the above vibrational assignment, although it is the most reasonable explanation of the observed vibrational spectrum. Our rotational analysis of the bands indicates that both of these states are in Coriolis resonance with another state or states which are not seen in our spectrum.
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33.20.Kf Visible spectra
33.20.Sn Rotational analysis

The rotational spectra, molecular structures, and 201Hg nuclear quadrupole coupling constants of HgHCl and HgDCl

J. A. Shea and E. J. Campbell

J. Chem. Phys. 81, 5326 (1984); http://dx.doi.org/10.1063/1.447675 (10 pages) | Cited 14 times

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High‐resolution rotational spectra of 16 isotopic species of the gas phase van der Waals complex HgHCl have been measured using pulsed Fourier‐transform microwave spectroscopy carried out in a Fabry–Perot cavity. The Hg–Cl distance is 4.097 Å in HgHCl and 4.112 Å in HgDCl, with the acid proton located between the two heavy atoms, analogous to the structures of previously studied rare gas‐hydrogen halide complexes. Based on this structure, an effective van der Waals radius of 1.99 Å for mercury in HgHCl is determined. 201Hg nuclear quadrupole coupling constants were measured for two complexes: χHg (201HgH 35Cl)=+5.993 (165) MHz, and χHg(201HgD 35Cl) =+7.789 (165) MHz. From these constants, and from a similar measurement for 201HgHC 15N, we obtain the first experimental estimate of the Sternheimer shielding constant in the mercury atom γ∞ =−47(7). Force constants and normal frequencies for the van der Waals vibrational modes were also calculated and compared with those of rare gas‐hydrogen chloride complexes.
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33.20.Bx Radio-frequency and microwave spectra
33.15.Dj Interatomic distances and angles
33.15.Mt Rotation, vibration, and vibration-rotation constants

Photoionization of vapor phase thallium and indium monohalides in the ultraviolet: Absolute cross sections and photofragment spectroscopy by photodetachment of I−

D. B. Geohegan, A. W. McCown, and J. G. Eden

J. Chem. Phys. 81, 5336 (1984); http://dx.doi.org/10.1063/1.447676 (16 pages) | Cited 9 times

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Absolute cross sections for the photoionization of thallium iodide (TlI) and thallium bromide (TlBr) at 193 nm (ℏω=6.4 eV) have been measured to be 2.4×10−17 and 2.2×10−17 cm2, respectively. An upper bound for the ionization cross section of indium monoiodide (InI) at 193 nm was determined to be 7×10−18 cm2. At 248 nm (ℏω=5.0 eV) and 351 nm (ℏω=3.5 eV), the TlI cross section has fallen to 2.6×10−18 and 1.5×10−19 cm2, respectively. The large cross section for TlI at 193 nm arises from photoionization of a bound molecular state. For InI at 6.4 eV and TlI at 5.0 and 3.5 eV, the molecule rapidly dissociates and the smaller cross sections are associated with photoionization of the metal atom. Further experiments combining two excimer lasers with a microwave absorption apparatus were conducted in order to determine the fraction of TlI molecules absorbing a 193 nm photon that produce Tl+–I− ion pairs. By photodetaching electrons from those I− ions remaining after an initial ultraviolet laser pulse, the branching ratio for ion pair production in TlI at 193 nm was measured to be 2%. Approximately 36% of the 193 nm photons absorbed by ground state TlI molecules result in the production of the Tl(7 2S1/2) species and 62% directly produce an excited TlI molecule. The implications of these results for existing atomic photodissociation lasers (Tl: 378 and 535 nm; In: 451 and 410 nm) and column IIIA metal film deposition are discussed.
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33.80.Eh Autoionization, photoionization, and photodetachment
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.20.Lg Ultraviolet spectra

Isolated C–H stretching vibrations of n‐alkanes: Assignments and relation to structure

Robert G. Snyder, A. L. Aljibury, Herbert L. Strauss, H. L. Casal, K. M. Gough, and W. F. Murphy

J. Chem. Phys. 81, 5352 (1984); http://dx.doi.org/10.1063/1.447677 (10 pages) | Cited 34 times

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The conformational/configurational dependence of the frequencies of the deuterium‐isolated C–H stretching modes of the gas‐phase alkanes C1, C2, n‐C3, n‐C4(t and g), n‐C5(tt and gt), cyclo‐C6, iso‐C4, and neo‐C5 are reported. Most of the isolated C–H frequencies were obtained from Raman spectra of specifically and randomly protonated deuterohydrocarbons. An extraordinarily precise correlation is found between the observed isolated C–H frequencies and the corresponding ab initio calculated C–H bond lengths. In the case of the n‐alkanes, the observed C–H frequencies tend to fall in clusters that are regularly spaced with an average separation of about 14.5±1 cm−1. The clustering occurs because the isolated C–H stretching frequencies are determined by the structure of the n‐alkane in the immediate vicinity of the C–H bond. The relation between frequency and local structure can be expressed in a simple way and used to predict the effect of conformational change.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

The occurrence and stability of trivalent zirconium in orthophosphate single crystals

M. M. Abraham, L. A. Boatner, J. O. Ramey, and M. Rappaz

J. Chem. Phys. 81, 5362 (1984); http://dx.doi.org/10.1063/1.447678 (5 pages) | Cited 9 times

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EPR spectroscopy has been used in investigations of the unusual 3+ valence state of zirconium. The EPR spectrum of Zr3+, which was initially observed as a parasitic signal in Fe‐doped single crystals of ScPO4, was definitively identified by preparing single crystals of ScPO4 doped with isotopically enriched (94.6%)91Zr. Single crystals of LuPO4 and YPO4 doped with both naturally abundant and isotopically enriched Zr were also grown and investigated. The EPR spectrum of Zr3+ could be observed at room temperature in the ‘‘as‐grown’’ single crystals of both ScPO4 and LuPO4; and, accordingly, the 3+ state is stable at room temperature in these hosts. The spectrum of Zr3+ in the YPO4 host could only be observed following a γ irradiation at 77 K, and this spectrum decayed rapidly with increasing temperature. Axial spin‐Hamiltonian parameters were determined for Zr3+ in all three hosts at a sample temperature of 77 K and at room temperature for the ScPO4 and LuPO4 hosts. In the case of the latter two hosts, the spin‐Hamiltonian parameters were found to exhibit a small temperature dependence. The observed g values were not accounted for by previously published second‐order expressions indicating that additional coupling mechanisms are operative.
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76.30.He Platinum and palladium group (4d and 5d) ions and impurities (Zr-Ag and Hf-Au)
28.41.Kw Radioactive wastes, waste disposal

The role of intersystem collisional transfer of excitation in the determination of N2 vibronic level populations. Application to B′ 3Σ−u–B 3πg band intensity measurements

William Benesch and Douglas Fraedrich

J. Chem. Phys. 81, 5367 (1984); http://dx.doi.org/10.1063/1.447679 (8 pages) | Cited 8 times

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This work constitutes a two‐part study of molecular nitrogen in laboratory electric discharges. In the first part, an investigation is undertaken of the phenomenon of the intersystem collisional transfer (ICT) of excitation (recently advanced as the process which gives rise to the reddening of type B aurora) in which ICT is established as a dominant mechanism controlling the distribution of vibronic level populations under discharge conditions. In particular, it is determined that there occur many pairs of vibronic levels in adjacent electronic states in which the pair partners attain essentially identical populations through the agency of collisional coupling. In the second part, the knowledge of completely shared populations is combined with the results of a series of measurements of emission band intensities in N2 to obtain transition probabilities and transition moments for the infrared afterglow system B′ 3Σ−u –B 3πg. A tabulation of transition probabilities and vibronic level lifetimes for this system is presented.
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33.50.Dq Fluorescence and phosphorescence spectra
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
52.80.Hc Glow; corona

Nitrogen K‐shell photoemission and Auger emission from N2 and NO

D. W. Lindle, C. M. Truesdale, P. H. Kobrin, T. A. Ferrett, P. A. Heimann, U. Becker, H. G. Kerkhoff, and D. A. Shirley

J. Chem. Phys. 81, 5375 (1984); http://dx.doi.org/10.1063/1.447680 (4 pages) | Cited 38 times

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The first gas‐phase photoelectron measurements near the nitrogen K edges of N2 and NO are reported. Shape‐resonance behavior is exhibited in the cross sections for both N 1s photoemission and N KVV Auger emission. The measured cross sections agree well with absorption and electron‐energy‐loss results, and with Stieltjes–Tchebycheff moment‐theory calculations (for N2) except for a small energy shift. The measured asymmetry parameters for N 1s photoemission also exhibit changes in the shape‐resonance region, but not as pronounced as those predicted by the multiple‐scattering method (MSM). Comparison of all of the results with the MSM calculations indicates that the shape‐resonance effects predicted by the MSM are higher in energy, and are narrower and more intense than those actually observed.
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33.60.+q Photoelectron spectra
33.20.Rm X-ray spectra
33.80.Eh Autoionization, photoionization, and photodetachment

Microwave spectrum, structure, and π conjugation of isocyanocyclopropane

William H. Taylor, Marlin D. Harmony, David A. Cassada, and Stuart W. Staley

J. Chem. Phys. 81, 5379 (1984); http://dx.doi.org/10.1063/1.447681 (5 pages) | Cited 5 times

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The microwave spectrum of the normal isotopic species of isocyanocyclopropane and its three unique mono‐substituted 13C isotopic varieties have been investigated in their natural isotopic abundances. For the normal isotopic species, Stark modulation and RFMDR techniques lead to the following rotational constants: A=15 827.303±0.009 MHz, B=3734.004±0.002 MHz, and C=3515.892±0.002 MHz. These data, along with those for the three isotopic species, lead to the following heavy atom structural parameters: C1C2=1.521±0.007 Å, C2C3=1.513±0.005 Å, C1N=1.377±0.008 Å, and C≡N=1.176±0.005 Å. To within a precision of ±1°, the C–N≡C group is linear and is inclined at an angle of 123.4±0.6° to the plane of the ring. The structural parameters are compared to those of related molecules and interpreted in terms of a frontier molecular orbital model for the π conjugation of the cyclopropyl ring.
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33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Dj Interatomic distances and angles

Chemical exchange effects in holographic relaxation spectroscopy

Charles S. Johnson

J. Chem. Phys. 81, 5384 (1984); http://dx.doi.org/10.1063/1.447682 (5 pages) | Cited 2 times

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Holographic relaxation spectroscopy combined with electrophoresis (EHRS) is suggested as a method for determining reaction rates in solution. This method is inherently more sensitive than electrophoretic light scattering (ELS) for small molecules and is selective since the molecules of interest are labeled. Equations are derived for the EHRS frequency spectrum in the presence of chemical exchange reactions, and the two‐site problem is worked out in detail as an illustration. Simulations of spectra are presented for intra and intermolecular exchange. It is shown that, under favorable conditions, electrophoretic mobilities of macromolecules in equilibrium with photochromic dyes can be determined without the necessity of covalent labeling.
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82.45.-h Electrochemistry and electrophoresis
82.20.Pm Rate constants, reaction cross sections, and activation energies
42.40.My Applications
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Systematic investigation of the Cooper minimum for the hydrogen halides

Thomas A. Carlson, Anders Fahlman, M. O. Krause, Timothy A. Whitley, and Frederick A. Grimm

J. Chem. Phys. 81, 5389 (1984); http://dx.doi.org/10.1063/1.447683 (6 pages) | Cited 23 times

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Angle‐resolved photoelectron spectroscopy has been carried out on the two outermost molecular orbitals of HBr using synchrotron radiation from a photon energy of 14 to 110 eV. Both partial cross sections σ and angular distribution parameters β have been determined experimentally. For comparison, calculations were also carried out on σ and β using the multiple scattering Xα method. Both the experimental and calculated results are discussed in terms of the Cooper minimum. Comparison is made with earlier results on HCl and HI and with results on the rare gases, which are isoelectronic with the hydrogen halides.
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33.60.+q Photoelectron spectra
33.80.Eh Autoionization, photoionization, and photodetachment
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