Formaldehyde as a semirigid bender: The rotation-inversion spectrum in its Ã1A2 excited state

The semirigid bender Hamiltonian [Bunker and Landsberg, J. Mol. Spectrosc.67, 374–385 (1977)] was used to fit the rotation-inversion energy level separations in the $\text{A}\text{?}{}^1\text{A}{}_2$ excited state of formaldehyde. We fix the r⁰(CH) bond length and allow the R(CO) bond length and (H?H) bond angle to vary with the inversion angle ρ. The fit to 64 rotation-inversion energies (with v₄ and J < 4) is significantly better with a standard deviation of 0.199 cm^?1 than when the rigid bender [Bunker and Stone, J. Mol. Spectrosc.41, 310–332 (1972)] is used. The barrier height to planarity is 358 cm^?1 and the equilibrium ρ_e = 34.7°. The CO bond length is found to decrease by 0.034 from 1.3670 Å and the H?H angle by about 6 from 122.4° as the molecular configuration changes from planar to pyramidal. The rigid bender model developed earlier by Moule and Rao for formaldehyde [J. Mol. Spectrosc.45, 120–141 (1973)] is then used to fit the 32 rotation-(out-of-plane) bending energy levels (with v₄ = 0 and 1) of the $\text{X}\text{?}{}^1\text{A}{}_1$ ground electronic state of H₂CO. For this, a simple potential consisting of quadratic and quartic terms is used and the standard deviation of the fit is 0.148 cm^?1.     

The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.     

The Ã1B2-X̃1A1 two-photon fluorescence excitation spectrum of 1,3-difluorobenzene

The $\text{A}\text{?}{}^1\text{B}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ system of 1,3-difluorobenzene has been observed using the technique of two-photon fluorescence excitation obtained with a pulsed dye laser. Calibration was achieved by a combination of the neon optogalvanic spectrum and etalon fringes. In circular, compared to linear, polarization the bands divide into two groups, those which are B₂-A₁ and which retain their intensity with circular polarization, and those which are A₁-A₁ and lose about 60% of their intensity under the same conditions. These two kinds of bands also show characteristic rotational contours. All of the A₁-A₁ bands whose assignments are established obtain their intensity through vibronic interaction in which the vibration ν′₂₅ (ν′₁₄ in the Wilson numbering) mixes the $\text{A}\text{?}$ with, presumably, the $\text{X}\text{?}$ state. There is an important Fermi resonance between the 9¹ and 10¹11¹ levels. Parts of the one-photon absorption spectrum have been photographed to identify sequences associated with the 0₀⁰ band for comparison with those observed in the two-photon spectrum, and to search for bands involving odd quanta of b₂ vibrations, including ν′₂₅ (ν′₁₄); none was found.     

Giant kondo resistivity in (La, Ce) B6

The electrical resistivity of the system $\text{(}\text{La}\text{, Ce)B}{}_6$ has been measured in the temperature range 0.04–300 K. The alloys show a Kondo minimum at about 20 K and a strong increase of the resistivity with decreasing temperature. The low temperature increase of the resistivity due to the Kondo effect of a sample containing 1, 2 at.% is about half as large as the room temperature resistivity of LaB₆. The Kondo temperature T_K of $\text{(}\text{La}\text{, Ce)B}{}_6$ was found to be 1.1 ± 0.2 K by comparison of the experimental results with theoretical predictions of the resistance anomaly associated with the formation of the spin-compensated state.     

Molecular three-body approach to Λ9Be and Σ9Be hypernuclei

The dependence of the low-lying spectra of ${}_{\mathrm{\Lambda ,\; \Sigma }}{}^9\text{Be}$ hypernuclei on hyperon-α interaction in the molecular α + α + Λ(Σ) scheme has been studied. A suggestion is made for obtaining the strengths of both p-wave and spin-orbit Λ-α interactions from the experimental ${}_{\mathrm{\Lambda }}{}^9\text{Be}$ spectrum. A relation between the Σ⁰-binding energies $\text{B}{}_{\mathrm{\Sigma }}\text{(}{}_{\mathrm{\Sigma }}{}^9\text{Be}\text{)}$ and $\text{B}{}_{\mathrm{\Sigma }}\text{(}{}_{\mathrm{\Sigma }}{}^9\text{He}\text{)}$ has been established and on its basis a prediction is made about a possible binding energy of ${}_{\mathrm{\Sigma }}{}^5\text{He}$.     

The γ-decay of the g92 analogue state in 59Cu

An investigation of the γ-decay of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ analogue state in ⁵⁹Cu has been performed using the ⁵⁸Ni(p, γ)⁵⁹Cu reaction. The (p, γ) excitation function has been taken in the range E_p = 3450–3650 keV. The decay schemes of the (p, γ) resonances at E_p = 3483, 3532 and 3547 keV, measured with Ge(Li) detectors, lead to eight new levels in ⁵⁹Cu with excitation energies between 1.8 and 4.7 MeV and to spin assignments of several states. The spins of the first two resonances are found to be ($\text{1}\text{2}$, $\text{3}\text{2}$) and ($\text{5}\text{2}$). The spin of the E_p = 3547 keV resonan is, from angular distributions, uniquely determined to be $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ and this state is found to be the unfragmented analogue state of the $\text{E}{}^1\text{= 3.062}\text{MeV}$, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ parent state in ⁵⁹Ni. The measured complete decay scheme of this resonance shows that its isovector M1 decay is in disagreement with all existing theoretical predictions.     

The HH1Σg+ state of hydrogen: Adiabatic calculation of vibronic states in H2, HD,and D2

The nuclear-mass-dependent diagonal corrections to the electronic energies of the $\text{H}\text{H}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ state of hydrogen are computed in the range 1.25 ≤ R ≤ 11 a.u. The correction energy goes through a pronounced peak near R = 3 a.u., which is discussed in terms of the character of the electronic wavefunction. The rovibrational structures of H₂, HD, and D₂ in the adiabatically corrected double-minimum potential curves of these isotopes in the $\text{H}\text{H}$ state are presented. Comparison with experimental data indicates the presence of appreciable nonadiabatic perturbations.     

Attenuation of traffic noise indices Leq and LN

Analysis of the attenuation of $\text{L}{}_{\mathrm{eq}}$ and $\text{L}{}_{\mathrm{N}}$ values with distance over grassland from a line of moving traffic indicates that the noise sources effectively radiate energy in the horizontal plane with a distance term different from the commonly assumed inverse square law. This requires an adjustment to the angular corrections for partial screening which now become dependent on the noise index being measured. The attentuation of traffic noise by a wooden fence structure around a suburban house has also been investigated. Shielding effects caused by various components were isolated as the fence structure was sequentially demolished. The shape of the sound field behind the finite length of front fence was deduced, for the various $\text{L}{}_{\mathrm{N}}$ values, by using the amended angular corrections.     

Reexamination of the I2 spectrum near the B(3Π0u+) state dissociation limit

The disagreement of Danyluk and King's (Chem. Phys.25, 343 (1977)) rotational constants for levels lying near the dissociation limit of B-state I₂ with the mechanical behavior predicted by near-dissociation theory is investigated. The discrepancies are shown to be much too large to be explained by either the neglect of centrifugal distortion effects in the original analysis or by rotational or spin-rotation coupling to a nearby repulsive 1_u state. These differences are therefore attributed to experimental error, a conclusion which is confirmed by more recent experimental results. A reanalysis of the best available data for levels near the dissociation limit of B-state I₂ then yields improved values for the B-state dissociation limit $\text{D}$ = 20 043.16 (±0.02) cm^?1 of the vibrational index at dissociation v_$\text{D}$ = 87.32 (±0.04) and of the long-range potential constant $\text{C}{}_5\text{= 2.88 (±0.03) × 10}{}^5\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^5$. This in turn implies a slightly improved ground-state dissociation energy of $\text{D}$₀ = 12 440.18 (±0.02) cm^?1.     

Rotational analysis of a red A′ 2Σ+-X 2Πi system of CuO

High dispersion rotational analysis of a red CuO band system has led to the identification of an $\text{A′}{}^2\text{Σ}{}^{\mathrm{+}}\text{-X}{}^2\text{Π}{}_{\mathrm{i}}$ transition. The anomalous appearance of the branches is due to a very large spin splitting of the ²Σ upper state. The influence of centrifugal distortion effects on this spin splitting (γ_D and γ_H parameters) is essential for explaining the band structure. A reassignment of electronic symmetries of all the ²Σ states of CuO is proposed.     

The Ã1A1-X̃1A1 two-photon fluorescence excitation spectrum of 1,2-difluorobenzene

The two-photon fluorescence excitation spectrum of 1,2-difluorobenzene was obtained with a tunable dye laser calibrated using a combination of the neon optogalvanic spectrum and etalon fringes. The spectrum consists only of A₁-A₁ bands but the use of linear and circular polarization divides the bands into two types. The 0⁰₀ type retains its intensity in circular polarization and, rotationally, shows little or no zero-rank contribution. The 5¹₀ (or 14¹₀) type loses much of its intensity in circular polarization and, rotationally, shows a large zero-rank contribution. These observations all accord with the trace of the two-photon transition tensor being close to zero for the 0⁰₀ type and large for the 5¹₀ type, the latter type being involved in vibronic interaction which mixes the $\text{A}\text{?}$ and $\text{X}\text{?}$ states. There is strong evidence for Fermi resonance between the 5¹ and 6¹10¹ levels. Parts of the one-photon absorption spectrum have been photographed to aid sequence identification and also to look for the 5¹₀, A₁-A₁ transition. This transition is not observed: nor is there any evidence for intensity stealing by b₂ vibrations.     

The 12C(13C, α)21Ne reaction: High-spin states,resonances and coherence widths

Excitation functions were measured for states of ²¹Ne populated by the ${}^{12}\text{C}\text{(}{}^{13}\text{C}\text{, α)}$ reaction over the bombarding energy range E_lab = 18.2–32.0 MeV (18.4–27.0 MeV) at θ_lab = 7°(25°) in in 200 keV steps, and average coherence widths of states and the moment of inertia of the compound nucleus ²⁵Mg were obtained from these excitation functions. A statistical analysis of these data was performed. Angular distributions for states in ²¹Ne to 10 MeV in excitation energy were measured at θ_lab = 7°, 18°, 28° and 43° at bombarding energies from 29.0 to 31.0 MeV in 400 keV steps. These data along with Hauser-Feshbach predictions allow us to suggest spins for some states as well as to suggest possible candidates for rotational bands in ²¹Ne.     

The mechanism of 5D3−5D4 cross-relaxation in Y3Al5O12: Tb3+

The ${}^5\text{D}{}_3\text{?}{}^5\text{D}{}_3$ cross-relaxation of YAG:Tb³⁺ has investigated by analysis of the ⁵D₃ decay curve as a function of Tb³⁺ concentration. This technique is a more sensitive test of the mechanism than relative intensity measurements alone. It is shown that the relaxation is predominantly dipole-dipole in character (R₀ ～ 1.3nm), and insensitive to temperature. The population of the ⁵D₄ state following high energy excitation occurs almost entirely via cross-relaxation from the ⁵D₃ state.     

Analysis of the perturbed NO22B2 ← 2A1 system in the 591.4- to 592.9-nm region based on sub-Doppler laser spectroscopy

Sub-Doppler excitation spectra of NO₂, covering four vibronic bands within the spectral range from 16 861 to 16 903 cm^?1, were measured with a resolution of down to 10 MHz in a collimated supersonic molecular beam. Unambiguous assignment of all prominent lines in the 42-cm^?1-wide interval of the ${}^2\text{B}{}_2\text{←}{}^2\text{A}{}_1$ excitation spectrum was achieved by recording for each excitation line at least four vibrational bands of the corresponding fluorescence spectrum with completely resolved rotational lines. From least-squares fits to the line positions in the excitation spectra the rotational, fine, and hyperfine structure of the ²B₂ state was analyzed. A perturbation analysis, based on information from both types of spectra, confirms earlier models of vibronic coupling with high-lying vibrational levels of the ²A₁ ground state and gives evidence for spin-orbit coupling. Possible models are discussed which may explain the observed perturbations.     

Near-infrared bands of S2: 3Πgi-3Σu+ system

Vibrational and rotational analyses of the near-infrared bands of S₂ lying in the region 7440–8085 Å are reported. They form a new band system involving a ${}^3\text{Π}{}_{\mathrm{gi}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ transition and arise from the same initial ³Π_gi state of the ³Π_gi-³Δ_ui band system reported earlier. The analyses of the bands of this system due to the isotopic molecules ³²S³⁴S and ³⁴S₂ are also reported.     

The H2+ ion in an intense magnetic field: Improved adiabatic approximations

We study the ground state binding energy of the $\text{H}{}_2{}^{\mathrm{+}}$ ion in an intense magnetic field. Our calculations are based on improved forms of the adiabatic approximation. We calculate the binding energy, the equilibrium internuclear separation and the zero point energies of nuclear vibrations both parallel and perpendicular to the magnetic field. Comparison of our results with those obtained from the static adiabatic approximation and from variational calculations shows a substantial improvement.     

20Ne + n → 21Ne(T = 32) resonances

$\text{T =}\text{3}\text{2}$ resonances in ²¹Ne have been studied in measurements of the total neutron cross section of ²⁰Ne using the 190 m neutron time-of-flight facility of the Karlsruhe Isochronous Cyclotron. The high time-of-flight resolution of 6.6 ps/m enabled the study of sharp $\text{T =}\text{3}\text{2}$ resonances in ²¹Ne with an effective energy resolution of up to 4000. Five $\text{T =}\text{case3}\text{2}$ levels have been observed as sharp resonances allowing the precise determination of total width Λ, partial decay with Λ_no and resonance energy E_R. The c.m. resonance parameters of the first $\text{T =}\text{3}\text{2}$ state in ²¹Ne are E_R = 2098.6 ± 0.3 keV, Λ = 2.2 ± 0.5 keV and Λ_no = 0.21 ± 0.05 keV. Upper limits for the partial decay widths are deduced for those $\text{T =}\text{3}\text{2}$ levels which do not appear as resonance anomalies. A search for additional $\text{T =}\text{3}\text{2}$ states was undertaken. The resonance energies are discussed in the framework of the isbobaric mass multiplet equation. The decay widths are compared with shell-model predictions of isospin mixing and the systematics of isospin-non-conserving particle decays.     

The 16O + p → 17F (T = 32) resonances at Ep = 11.26,12.71 and 14.57 MeV

Excitation functions for ¹⁶O+p reactions have been measured with high energy resolution in the region of the first, second and seventh $\text{T =}\text{3}\text{2}$ resonances in ¹⁷F at extreme backward angles. The observed resonance shapes have been analyzed with a single-level resonance formula taking the off-resonance spin-flip amplitude into account. The resonance parameters of the ¹⁷F first $\text{T =}\text{3}\text{2}$ state studied with special emphasis are E_x = 11193.3 ± 2.3 keV, Γ = 200 ± 40 eV and Γ_p0 = 19 ± 3 eV. This result and other results are compared with previous studies and theoretical predictions. The comparison with data of the mirror nucleus ¹⁷O is discussed with respect to the observed charge asymmetry of the isospin-forbidden particle decay widths.     

Dynamical supersymmetry in 196Pt and 197Au

The excitation energies, reduced E2 transition probabilities and spectroscopic factors in the (${}^3\text{He, d}$) reaction for the levels with positive parity in ${}^{197}\text{Au}$ up to about 1 MeV, together with the corresponding data for ${}^{196}\text{Pt}$, are shown to be in overall agreement with the predictions of a dynamical supersymmetry scheme recently proposed for nuclei in this mass region.     

On the question of fine structure in νp and EK for 233U and 235U

The question of fine structure in the variation of the average number of prompt neutrons, $\text{ν}{}_{\mathrm{<mtext>p</mtext>}}$, emitted per fission with energy in the neutron fission of ²³³U and ²³⁵U has been examined. Consistent structure has been found in measurements of both $\text{ν}{}_{\mathrm{<mtext>p</mtext>}}\text{and}\text{E}{}_{\mathrm{<mtext>K</mtext>}}$ (the average total fission fragment kinetic energy) for ²³³U. Channel analysis of the neutron fission cross section of ²³³U allows the structure to be calculated quantitatively provided the collective energy at the second hump in the fission barrier is weakly coupled to the nuclear degrees of freedom at scission. A similar calculation for neutron fission of ²³⁵U supports the case for the absence of fine structure in $\text{ν}{}_{\mathrm{<mtext>p</mtext>}}\text{and}\text{E}{}_{\mathrm{<mtext>K</mtext>}}$ for this nucleus.