Supersonically cooled hydronium ions in a slit-jet discharge: high-resolution infrared spectroscopy and tunneling dynamics of HD2O+

Jet-cooled high-resolution infrared spectra of partially deuterated hydronium ion (HD2O+) in the O-H stretch region (nu3 band) are obtained for the first time, exploiting the high ion densities, long absorption path lengths, and concentration modulation capabilities of the slit-jet discharge spectrometer. Least-squares analysis with a Watson asymmetric top Hamiltonian yields rovibrational constants and provides high level tests of ab initio molecular structure predictions. Transitions out of both the lower (nu3(+)<--0(+)) and the upper (nu3(-)<--0(-)) tunneling levels, as well as transitions across the tunneling gap (nu3(-)<--0(+)) are observed. The nu3(-)<--0(+) transitions in HD2O+ acquire oscillator strength by loss of D(3h) symmetry, and permit both ground-state-[27.0318(72) cm(-1)] and excited-state-[17.7612(54) cm(-1)]-tunneling splittings to be determined to spectroscopic precision from a single rovibrational band. The splittings and band origins calculated with recent high level ab initio six-dimensional potential surface predictions for H3O+ and isotopomers [X. C. Huang, S. Carter, and J. M. Bowman, J. Chem. Phys. 118, 5431 (2003); T. Rajamaki, A. Miani, and L. Halonen, J. Chem. Phys. 118, 10929 (2003)] are in very good agreement with the current experimental results.     

A uniform approximation for one-dimensional matrix elements

A general expression for one-dimensional perturbation integrals is derived, which requires no knowledge of the radial wavefunctions. It is shown to generalize and to unify all available semi-classical approximations, and, further, to reduce to a number of known results for the curve-crossing problem and to the Jackson-Mott for the Landau-Teller vibrational relaxation model.     

Aromatic Superhalogens

No organic molecules with electron affinities near or above those of halogens are known. We show for the first time that aromaticity rules can be used to design molecules with electron affinities far exceeding those of halogen atoms either by tailoring the ligands of cyclopentadienyl or by multiple benzoannulations of cyclopentadienyl in conjunction with the substitution of CH groups with isoelectronic N atoms. Results based on density functional theory revealed that the electron affinities of some of these organic molecules can reach as high as 5.59 eV, thus opening the door to new class of superhalogens that contain neither a metal nor a halogen atom.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Ultrasonic heating of the skull

Comparatively simple analysis shows that diagnostic ultrasound devices, in some cases, may approach output levels that can produce significant heating of tissues, particularly if the propagation path includes bone. Experimental tests of these predictions using rodents show that temperature increments of the order of 3 degrees C/W/cm2 are produced in skull bone with sharply focused fields at medically relevant frequencies.     

Binding and photodissociation of CO in iron(II) complexes for application in positron emission tomography (PET) radiolabelling

(R-DAB)FeI(2) complexes containing bidentate diimide ligands (R-DAB = RN=CH-CH=NR; R = (i)Pr, c-C(6)H(11)) have been investigated for their ability to react with carbon monoxide to form iron(II) dicarbonyl complexes, (R-DAB)FeI(2)(CO)(2). Solution IR spectroscopy revealed two νCO stretches between 2000 and 2040 cm(-1) corresponding to a cis-arrangement of the carbonyl ligands around the iron. Photochemical decarbonylation was achieved by UV irradiation (365 nm), which occurred within 5 min as evidenced by solution IR spectroscopy. (c-C(6)H(11)-DAB)FeI(2) has been characterised by X-ray crystallography. Reactions using (11)C-labelled carbon monoxide were investigated and revealed that both (R-DAB)FeI(2) species were not effective as trapping complexes due to the low concentrations of [(11)C]CO used in these experiments. A Fe(TPP)(THF)(x) (TPP = tetraphenylporphyrin) complex was investigated with unlabelled CO and the monocarbonyl adduct Fe(TPP)(THF)CO was formed in situ as identified by IR spectroscopy (νCO = 1966 cm(-1)) yet was stable to CO loss upon UV irradiation. Carbonylation reactions of in situ-generated Fe(TPP)(THF)(x) using [(11)C]CO revealed that 97% of the [(11)C]CO stream could be trapped in one pass of the gas at room temperature and at atmospheric pressure.     

Vibrational-electronic coupling in IrF6, OsCl6 2− and IrCl6 2−

The results obtained in a previous paper [1] for an unsymmetric regular model are applied to solid hydrogen at low temperatures when the lattice structure and the quadrupole-quadrupole interaction make the interaction energies non-isotropic. It is shown that, as for the lattice structures with isotropic interactions, no second-order transition is likely to occur through a cooperative rotational effect. The possible occurrence of spatial ordering on sub-lattices is discussed. It is found that such ordering is unlikely to occur at low temperatures on the face-centred cubic lattice, but that on the hexagonal close-packed lattice (which is the probable crystal structure) there is a second-order transition to an ordered state. Using a zeroth-order approximation the temperature at which this transition occurs in pure ortho-hydrogen is found to be 5·8°k.     

Predissociation and photodissociation of IBr

The observed predominance of excited Br(² P _1/2) atoms in the nearultra-violet photodissociation products of IBr is shown to be quantitatively consistent with an intermediate coupling regime in the visible absorption region, which invalidates the traditional interpretation of the B′(O ⁺) state as a new Born-Oppenheimer state arising from a strongly avoided potential curve crossing. A general theory of predissociation at intermediate coupling, covering the positions, intensities and widths of the spectral lines, shows that both diabatic and adiabatic characteristics must be taken into account. The presence of a sharp level is predicted at any coincidence between an adiabatic and a diabatic term value with the same J value, and the spacing between neighbouring lines is shown to depend on an average between the diabatic and adiabatic rotational constants. The theory is successfully applied to the B(³Π _{o ⁺} ) and B′(O ⁺) states of IBr, and potential curves for the two states are reported. The analysis is consistent with the following curve crossing parameters r_x = 3·220 Å, E_x = 16 915 cm^-1, V ₁₂ = 170 cm^-1, and ΔF = 9178 cm^-1 Å^-1, and with the following spectroscopic constants for the B′(O ⁺) state of IBr⁷⁹:

     

Quantum monodromy and molecular spectroscopy

Monodromy (or once round) is a classical property of integrable dynamical systems in two or more degrees of freedom, which imposes a characteristic pattern on the quantum mechanical eigenvalue distribution. This article explains the connection by showing how the presence of an isolated critical point of the Hamiltonian leads to a classical action function that is multi-valued with respect to energy and angular momentum. Consequently, by the Bohr correspondence principle between actions and quantum numbers, there can be no uniquely defined global system of quantum numbers. Implications for the interpretation of highly excited molecular spectra are brought out by reference to quasi-linear molecules, which transfer one degree of freedom from rotational to vibrational motion during the excitation process. Emphasis is placed on the simplest examples, while a brief resumé of the wide scope of the quantum monodromy phenomenon is given in the final section.     

Periodic-type functionals and their extensions

Let Ω denote a simply connected domain in the complex plane and let $\text{K[Ω]}$ be the collection of all entire functions of exponential type whose Laplace transforms are analytic on Ω′, the complement of Ω with respect to the sphere. Define a sequence of functionals $\text{{L}{}_{\mathrm{n}}\text{}}\text{on}\text{K[Ω]}$ by $\text{L}{}_{\mathrm{n}}\text{(f) =}\text{1}\text{2πi}\text{∝}{}_{\mathrm{\Gamma }}\text{g}{}_{\mathrm{n}}\text{(ζ) F(ζ) dζ}$, where F denotes the Laplace transform of f, Γ ? Ω is a simple closed contour chosen so that F is analytic outside and on Ω, and g_n is analytic on Ω. The specific functionals considered by this paper are patterned after the Lidstone functions, L_2n(f) = f⁽²ⁿ⁾(0) and L_{2n + 1}(f) = f⁽²ⁿ⁾(1), in that their sequence of generating functions {g_n} are “periodic.” Set g_{pn + k}(ζ) = h_k(ζ) ζ^pn, where p is a positive integer and each h_k (k = 0, 1,…, p ? 1) is analytic on Ω. We find necessary and sufficient conditions for $\text{f ∈ k[Ω]}\text{with}\text{L}{}_{\mathrm{n}}\text{(f) = 0 (n = 0, 1,…)}$. DeMar previously was able to find necessary conditions [7]. Next, we generalize {L_n} in several ways and find corresponding necessary and sufficient conditions.