On the possibility to measure the π0→γγ decay width and the γ?γ→π0 transition form factor with the KLOE-2 experiment

A possibility of KLOE-2 experiment to measure the width \varGamma_{p⁰ ?gg}\varGamma_{\pi^{0} \to\gamma\gamma} and the π ⁰ γγ ^∗ form factor F(Q ²) at low invariant masses of the virtual photon in the space-like region is considered. This measurement is an important test of the strong interaction dynamics at low energies. The feasibility is estimated on the basis of a Monte-Carlo simulation. The expected accuracy for \varGamma_{p⁰ ?gg}\varGamma_{\pi^{0} \to\gamma\gamma} is at a per cent level, which is better than the current experimental world average and theory. The form factor will be measured for the first time at Q ²≤0.1 GeV² in the space-like region. The impact of these measurements on the accuracy of the pion-exchange contribution to the hadronic light-by-light scattering part of the anomalous magnetic moment of the muon is also discussed.     

Kinetics of the apparent isothermal and non-isothermal crystallization of the α-Fe phase within the amorphous Fe81B13Si4C2 alloy

Kinetics of the apparent isothermal and the non-isothermal crystallization of α-Fe phase within the amorphous Fe₈₁B₁₃Si₄C₂ alloy were investigated by an X-ray diffraction (XRD) and by a differential scanning calorimetry (DSC). It was established that the apparent isothermal crystallization of α-Fe phase within amorphous Fe₈₁B₁₃Si₄C₂ alloy could be described by the Johnson-Mehl-Avrami (JMA) kinetic model (with parameter n_iso=4.0). The apparent isothermal crystallization process includes a constant rate of nucleation and three-dimensional growth of nuclei. The results of X-ray diffraction (XRD) data of the isothermally crystallized samples confirmed the above established kinetic model. From the kinetic analysis of the non-isothermal crystallization of the α-Fe phase within this amorphous alloy, it was concluded that the autocatalytic two-parameter Šesták-Berggren (SB) reaction model (with kinetic exponents M=0.72 and N=1.02) describes well the studied process under the given conditions. The non-isothermal crystallization process involves the constant nucleation rate of stable nuclei with additional secondary two-dimensional (surface) nucleation and overlapping of the growing nuclei on account of the non-isothermal activation.     

Perspectives for the measurement of Ds+ mesons via?the?Ds+ →K+K?π+ channel in the ALICE experiment

Heavy quarks, such as charm, are produced in hard scatterings in the early stages of high energy nucleus-nucleus collisions and are expected to be a powerful tool to investigate the properties of the quark gluon plasma (QGP). The tracking detectors of the ALICE apparatus will allow to track and identify particles in central rapidity range down to low P _t . Among D mesons it would be particularly interesting to measure D _s yield via an exclusive hadronic decay channel because it could help to disentangle different hadronization mechanisms. The possibility of reconstructing the D _s meson through its D _s ⁺→K ⁺ K ⁻ π ⁺ decay channel in the central barrel was studied. The problem considered is characterized by the comparatively low yield of the D _s mesons against the huge amount of combinatorial background. Different kinematic and topological cuts have been studied in order to increase the signal-to-background ratio and the statistical significance. In addition, D _s mesons preferentially decay through intermediate resonant states and this fact can improve the separation of signal from background. Results of cut parameters tuning and values of significance for an analysis performed on simulated data are presented.     

CO2 and N2O laser Stark spectroscopy of the ν1 band of the ClO2 radical

The ν₁ fundamental band of the ClO₂ radical has been studied by means of the 10.6-μm CO₂ and N₂O laser Stark spectroscopy. More than 250 and 150 Stark resonances were assigned for the ³⁵ClO₂ and ³⁷ClO₂ species, respectively, and were analyzed together with the recent microwave and laser-microwave double resonance results to give molecular constants including spin-rotation interaction constants. The ν₁ band origins and electric dipole moments both in the ground and ν₁ states were determined accurately

     

5.

Measurement of the decayτ^? →ρ^?ν_τ     

H. Albrecht  H. Ehrlichmann  T. Hamacher  R. P. Hofmann  T. Kirchhoff  A. Nau  S. Nowak  H. Schr?der  H. D. Schulz  M. Walter  et al. 《Zeitschrift fur Physik C Particles and Fields》1992,56(3):339-345

An analysis of the decay ^--0 v has been performed using the ARGUS detector at the DORIS II storage ring. The branching ratio has been determined to be Br(^--0 v =(22.6±0.4±0.9)%. The shape of the ^-0 invariant mass spectrum is found to be in good agreement with the predictions obtained using the conserved vector current (CVC) hypothesis, suggesting that the ^-0 system is produced in aJ ^P=1^– state. An analysis of the measured decay angular distribution of the pions with respect to the flight direction of the ^-0 system demonstrates the vector nature of the coupling at the v vertex. With the assumption of zerov mass thev spin has been shown to be .Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51 P     

6.

Stimulated Emission Pumping Spectroscopy of SiH₂: First Observation of the Spin-Orbit Interaction between the X?A₁ and the ãB₁ States     

Haruki IshikawaYasuhiko Muramoto  Naohiko Mikami 《Journal of Molecular Spectroscopy》2002,216(1):90-97

Stimulated emission pumping spectra of the ùB₁-X?¹A₁ transition of the SiH₂ radical were observed in order to obtain information about the ã³B₁ state through the spin-orbit interaction. The vibrational level structure of the X? state, which is the basis for the present observation of the triplet state, was well described with a polyad structure, in which both the 1ν₁ : 2ν₂ Fermi and the 2ν₁ : 2ν₃ Darling-Dennison anharmonic resonances were considered. In the P=10 polyad, four sets of spin-orbit perturbations were observed for the first time. The triplet state observed at about 9640 cm⁻¹ from the (000) level of the X? state was tentatively assigned as the ã³B₁ (030) level. An analysis of the spin-orbit interaction showed that the interaction energies of the spin-orbit coupling are 0.73-3.13 cm⁻¹. This value is rather smaller than that expected based on the comparison with CH₂. This is considered to be due to poor overlap between the vibrational wave functions in the ã and the X? state.     

7.

Stretch-Bender Calculations of the Rovibronic Energies in the Excited, ÃA₁, Electronic State of NH₂ and of the Near-Resonant High-Lying Levels of the X?B₁ State     

Geoffrey DuxburyAlexander Alijah 《Journal of Molecular Spectroscopy》2002,211(1):31-57

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the rovibronic energies in the region where the vibronic states of the excited òA₁ electronic state of NH₂ interact with near-resonant high-lying levels of the X?²B₁ state of NH₂. A detailed comparison has been made with the experimental measurements which were made of these rovibronic states, the majority of which are due to Ramsay, Vervloet, and their collaborators. We have shown that, as in our study of the vibronic levels of the X?²B₁ state below the barrier to linearity, in order to fit the variation of the effective vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A_SO must be increased from the earlier value of 50 cm⁻¹ of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm⁻¹. The impact of Fermi resonance, in both the òA₁ and X?²B₁ states, on the observed rovibronic structure has been assessed. The pattern of calculated spin-rovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally.     

8.

Renormalization of the band parameters owing to the phonon interaction in Bi₂Sr₂CaCu₂O_{8 ? x} and determination of the superconducting gap parameters from the temperature dependence of the superconducting current density in YBa₂Cu₃O₇     

M. V. Eremin  M. A. Malakhov  D. A. Sunyaev 《JETP Letters》2012,96(2):105-108

     

9.

Measurement of the photon structure functionF₂^γ in the reactione⁺e^?→e⁺e^?+hadrons at LEP     

R. Akers  G. Alexander  J. Allison  K. J. Anderson  S. Arcelli  A. Astbury  D. Axen  G. Azuelos  J. T. M. Baines  A. H. Ball  et al. 《Zeitschrift fur Physik C Particles and Fields》1994,61(2):199-208

We present measurements of the hadronic photon structure functionF ₂ (x), in twoQ ² ranges with mean values of 5.9 GeV² and 14.7 GeV². The data were taken by the OPAL experiment at LEP, with close to theZ ⁰ mass and correspond to an integratede ⁺ e ^– luminosity of 44.8 pb^–1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ ²>4 GeV². Our measurements extend to lower values ofx than any previous experiment, and no increase ofF ₂ (x) is observed.     

10.

Analysis of the decays ψ′ → J/ψπ⁺π^? and η′_c → η_cπ⁺π^? with the heavy-quark symmetry     

Zhi-Gang Wang 《The European Physical Journal A - Hadrons and Nuclei》2011,47(8):94

In this article, we study the decays ψ′ → J/ψπ ⁺ π ⁻ and η′_c → η _c π ⁺ π ⁻ by taking into account the chiral symmetry breaking effects, the final-state interactions and the heavy-quark symmetry. We can confront the predictions of the η′_c → η _c π ⁺ π ⁻ decay width and differential decay width with the experimental data in the future, and obtain powerful constraints on the chiral breaking effects and the final-state interactions, and test the heavy-quark symmetry.     

11.

Perturbations in the A¹Π-X¹Σ⁺ system of the BeO molecule     

H. Lavendy  B. Pouilly  J.M. Robbe 《Journal of Molecular Spectroscopy》1984,103(2):379-407

All perturbations observed by Lagerqvist (Thesis, University of Stockholm, 1948) in the A¹Π-X¹Σ⁺ transition have been assigned to a³Π₂, a³Π₁, and X¹Σ⁺ states. Vibrational and rotational constants of the a³Π state as well as electronic parameters for A ～ X, A ～ a, and a ～ X interactions have been determined.

		35ClO2		37ClO2
$\text{ν}{}_0$		945.592 357(60)		939.602 909(66)		cm?1
μ′		1.788 39(13)		1.788 46(15)		D
μ″		1.791 95(10)		1.792 10(13)		D
δμ		?0.003 56(18)		?0.003 64(26)		D

     

12.

An experimental study of the processγγ→π⁺π^?     

H. -J. Behrend  L. Criegee  J. H. Field  G. Franke  H. Jung  J. Meyer  J. H. Peters  O. Podobrin  V. Schr?der  G. G. Winter  et al. 《Zeitschrift fur Physik C Particles and Fields》1992,56(3):381-390

     

13.

Renner-Teller and Spin-Orbit Interactions between the ÃA₁ and the X?B₁ States of NH₂: The Stretch-Bender Approach     

Alexander Alijah  Geoffrey Duxbury 《Journal of Molecular Spectroscopy》2002,211(1):7-15

The stretch-bender model, developed originally to describe the effects of stretch-bend interactions and Renner-Teller coupling in symmetrical triatomic molecules, has been extended to incorporate the effects of spin-orbit interaction and of overall rotation. A comparison is made between the treatment of spin-orbit interaction and of overall rotation in our model and in the MORBID approach of P. Jensen, M. Brumm, W. P. Kraemer, and P. R. Bunker (J. Mol. Spectrosc.171, 31-57 (1995)).     

14.

Microwave spectroscopy of the ν₈-ν₆ band of diacetylene     

Keiji Matsumura  Tohru Etoh  Takehiko Tanaka 《Journal of Molecular Spectroscopy》1981,90(1):106-115

Vibration-rotation transitions of diacetylene between the first excited states of the ν₆ (CCH symmetric bending) and the ν₈ (CCH antisymmetric bending) vibrations were observed with a Stark modulation microwave spectrometer. The rotational, centrifugal distortion and l-type doubling constants of the two vibrational states were determined as follows with 2.5 σ uncertainties in parentheses.

	Reciprocal centimeters
	Te	ωe	ωexe	Be	αe	re (Å)
a3Π	8574	1132	8.4	1.3675	?0.0168	1.4623

     

15.

Constraints on the Z-Z′ mixing angle from data measured for the process e⁺e^? → W⁺W^? at the LEP2 collider     

Vas. V. Andreev  A. A. Pankov 《Physics of Atomic Nuclei》2012,75(1):76-89

An analysis of effects induced by new neutral gauge Z′ bosons was performed on the basis of data from the OPAL, DELPHI, ALEPH, and L3 experiments devoted to measuring differential cross sections for the process of the annihilation production of pairs of charged gauge W ^± bosons at the LEP2 collider. By using these experimental data, constraints on the Z′-boson mass and on the angle of Z-Z′ mixing were obtained for a number of extended gauge models.     

16.

Analysis of the hot bands in the 2ν₉ band region of propyne-d₃     

Geetha Rajappan 《Journal of Molecular Spectroscopy》2004,224(2):107-113

The rovibrational spectrum of 2ν₉ band of CD₃CCH is overlapped by two prominent hot bands identified as (2ν₉⁰+ν₁₀^±1)(E)←ν₁₀^±1(E) and 3ν₉^±1(E)←ν₉^±1(E), where ν₁₀ and ν₉ are the degenerate CCC and CCH bending fundamental vibrations, respectively. Assignment of lines to the transitions of these hot bands were carried out with the help of the high-resolution spectra recorded at ∼195 K and at room temperature. Molecular parameters for these hot bands have been obtained from the rotational analysis of the partially resolved K-structure lines. Only Q-head of the third hot band , originating from the lower 2ν₁₀ state could be identified.     

17.

Stretch-Bender Calculations of the Rovibronic Energies in the X?B₁ Electronic Ground State of NH₂     

Alexander Alijah  Geoffrey Duxbury 《Journal of Molecular Spectroscopy》2002,211(1):16-30

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the X?²B₁ state of NH₂ up to the barrier to linearity of this state. A detailed comparison has been made with experimental measurements of these rovibronic states, the majority of which are due to Vervloet and his collaborators. We have shown that, in order to fit the variation of the vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A_SO, must be increased from the earlier value of 50 cm⁻¹ of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm⁻¹. Evidence has also been provided for the large quenching of the spin-orbit coupling as the molecule bends, reflected in the large valuee of g_K=6 cm⁻¹. The pattern of calculated spinrovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally.     

18.

The simulation of infrared bands from the analyses of rotational spectra: the 2ν₉-ν₉ and ν₅-ν₉ hot bands of HNO₃     

D.T. Petkie  B.P. Winnewisser  R.A.H. Butler  F.C. De Lucia 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,92(2):129-141

The results of millimeter and submillimeter wave rotational spectroscopy are used to simulate the complex structure of the 2ν₉-ν₉ and ν₅-ν₉ hot bands. The comparison data were obtained with a high-resolution Bruker FTIR. The combination of the quality of these data and the complexity of the spectra of these interacting states represents a stringent test for the simulation. It is shown that the agreement is very good and that this approach is generally advantageous. From this simulation, the ratios of the transition dipole moments for the 2ν₉-ν₉ and ν₅-ν₉ hot bands with respect to the ν₉ fundamental band were found to be 1.38(11) and 0.67(20), respectively. Using these results, the calculated integrated band intensities for the hot bands at were determined to be and . These results were used to successfully simulate high-resolution stratospheric spectra obtained from a balloon flight of the FIRS-2 spectrometer. The more general problem of the rotation-vibration database and the optimal use of both microwave and infrared data to define it is discussed. It is concluded that it is best if the combination of data takes place at the level of the original spectra.     

19.

High-resolution infrared and theoretical study of the fundamental bands ν₂, ν₄ and ν₉ and the c-Coriolis interacting dyad ν₅, ν₁₄ of 1,3,4-thiadiazole     

F. Hegelund  R. Wugt Larsen  M.H. Palmer 《Journal of Molecular Spectroscopy》2008,248(2):161-167

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C₂H₂N₂S, has been recorded with a resolution of ca. 0.003 cm⁻¹ in the 800-1500 cm⁻¹ spectral region. Five fundamental bands ν₂(A₁; 1391.9 cm⁻¹), ν₄(A₁; 964.4 cm⁻¹), ν₅(A₁; 894.6 cm⁻¹), ν₉(B₁; 821.5 cm⁻¹), and ν₁₄(B₂; 898.4 cm⁻¹) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν₄ and ν₉ bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν₅ and ν₁₄ bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant . The ν₂ band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν₁₀ + ν₁₄ band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.     

20.

H₂-broadening coefficients in the ν₂ and ν₄ bands of PH₃     

Jean-Pierre Bouanich  Jamel Salem  Jacques Walrand 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(2):195-205

H₂-broadening coefficients are measured for 41 transitions of PH₃ in the QR branch of the ν₂ band and the PP, RP, and PQ branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 2 to 16 and K from 0 to 11 are located between 995 and . The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. These coefficients γ₀(J,K) are found to decrease slightly on the whole as J increases and they decrease significantly for K values approaching or equal to J(J?4). The H₂-broadenings are also calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. The theoretical results are in satisfactory agreement with the experimental data and reproduce the J and K dependencies of the broadenings, but the decrease observed for the QR(J,K) transitions with K=J is notably overestimated.     

	$\text{B}{}_{\mathrm{v}}\text{(}\text{MHz}\text{)}$	$\text{D}{}_{\mathrm{v}}\text{(}\text{kHz}\text{)}$	$\text{q}{}_{\mathrm{v}}\text{(}\text{MHz}\text{)}$
$\text{ν}{}_6$	4391.3230(84)	0.582(154)	2.4830(32)
$\text{ν}{}_8$	4391.1921(94)	0.594(179)	2.4073(37)

Measurement of the decayτ? →ρ?ντ

An analysis of the decay ^--0 v has been performed using the ARGUS detector at the DORIS II storage ring. The branching ratio has been determined to be Br(^--0 v =(22.6±0.4±0.9)%. The shape of the ^-0 invariant mass spectrum is found to be in good agreement with the predictions obtained using the conserved vector current (CVC) hypothesis, suggesting that the ^-0 system is produced in aJ ^P=1^– state. An analysis of the measured decay angular distribution of the pions with respect to the flight direction of the ^-0 system demonstrates the vector nature of the coupling at the v vertex. With the assumption of zerov mass thev spin has been shown to be .Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51 P     

Stimulated Emission Pumping Spectroscopy of SiH2: First Observation of the Spin-Orbit Interaction between the X?A1 and the ãB1 States

Stimulated emission pumping spectra of the ùB₁-X?¹A₁ transition of the SiH₂ radical were observed in order to obtain information about the ã³B₁ state through the spin-orbit interaction. The vibrational level structure of the X? state, which is the basis for the present observation of the triplet state, was well described with a polyad structure, in which both the 1ν₁ : 2ν₂ Fermi and the 2ν₁ : 2ν₃ Darling-Dennison anharmonic resonances were considered. In the P=10 polyad, four sets of spin-orbit perturbations were observed for the first time. The triplet state observed at about 9640 cm⁻¹ from the (000) level of the X? state was tentatively assigned as the ã³B₁ (030) level. An analysis of the spin-orbit interaction showed that the interaction energies of the spin-orbit coupling are 0.73-3.13 cm⁻¹. This value is rather smaller than that expected based on the comparison with CH₂. This is considered to be due to poor overlap between the vibrational wave functions in the ã and the X? state.     

Stretch-Bender Calculations of the Rovibronic Energies in the Excited, ÃA1, Electronic State of NH2 and of the Near-Resonant High-Lying Levels of the X?B1 State

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the rovibronic energies in the region where the vibronic states of the excited òA₁ electronic state of NH₂ interact with near-resonant high-lying levels of the X?²B₁ state of NH₂. A detailed comparison has been made with the experimental measurements which were made of these rovibronic states, the majority of which are due to Ramsay, Vervloet, and their collaborators. We have shown that, as in our study of the vibronic levels of the X?²B₁ state below the barrier to linearity, in order to fit the variation of the effective vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A_SO must be increased from the earlier value of 50 cm⁻¹ of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm⁻¹. The impact of Fermi resonance, in both the òA₁ and X?²B₁ states, on the observed rovibronic structure has been assessed. The pattern of calculated spin-rovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally.     

Measurement of the photon structure functionF2γ in the reactione+e?→e+e?+hadrons at LEP

We present measurements of the hadronic photon structure functionF ₂ (x), in twoQ ² ranges with mean values of 5.9 GeV² and 14.7 GeV². The data were taken by the OPAL experiment at LEP, with close to theZ ⁰ mass and correspond to an integratede ⁺ e ^– luminosity of 44.8 pb^–1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ ²>4 GeV². Our measurements extend to lower values ofx than any previous experiment, and no increase ofF ₂ (x) is observed.     

Analysis of the decays ψ′ → J/ψπ+π? and η′c → ηcπ+π? with the heavy-quark symmetry

In this article, we study the decays ψ′ → J/ψπ ⁺ π ⁻ and η′_c → η _c π ⁺ π ⁻ by taking into account the chiral symmetry breaking effects, the final-state interactions and the heavy-quark symmetry. We can confront the predictions of the η′_c → η _c π ⁺ π ⁻ decay width and differential decay width with the experimental data in the future, and obtain powerful constraints on the chiral breaking effects and the final-state interactions, and test the heavy-quark symmetry.     

Perturbations in the A1Π-X1Σ+ system of the BeO molecule

All perturbations observed by Lagerqvist (Thesis, University of Stockholm, 1948) in the A¹Π-X¹Σ⁺ transition have been assigned to a³Π₂, a³Π₁, and X¹Σ⁺ states. Vibrational and rotational constants of the a³Π state as well as electronic parameters for A ～ X, A ～ a, and a ～ X interactions have been determined.

Renner-Teller and Spin-Orbit Interactions between the ÃA1 and the X?B1 States of NH2: The Stretch-Bender Approach

The stretch-bender model, developed originally to describe the effects of stretch-bend interactions and Renner-Teller coupling in symmetrical triatomic molecules, has been extended to incorporate the effects of spin-orbit interaction and of overall rotation. A comparison is made between the treatment of spin-orbit interaction and of overall rotation in our model and in the MORBID approach of P. Jensen, M. Brumm, W. P. Kraemer, and P. R. Bunker (J. Mol. Spectrosc.171, 31-57 (1995)).     

Microwave spectroscopy of the ν8-ν6 band of diacetylene

Vibration-rotation transitions of diacetylene between the first excited states of the ν₆ (CCH symmetric bending) and the ν₈ (CCH antisymmetric bending) vibrations were observed with a Stark modulation microwave spectrometer. The rotational, centrifugal distortion and l-type doubling constants of the two vibrational states were determined as follows with 2.5 σ uncertainties in parentheses.

Constraints on the Z-Z′ mixing angle from data measured for the process e+e? → W+W? at the LEP2 collider

An analysis of effects induced by new neutral gauge Z′ bosons was performed on the basis of data from the OPAL, DELPHI, ALEPH, and L3 experiments devoted to measuring differential cross sections for the process of the annihilation production of pairs of charged gauge W ^± bosons at the LEP2 collider. By using these experimental data, constraints on the Z′-boson mass and on the angle of Z-Z′ mixing were obtained for a number of extended gauge models.     

Analysis of the hot bands in the 2ν9 band region of propyne-d3

The rovibrational spectrum of 2ν₉ band of CD₃CCH is overlapped by two prominent hot bands identified as (2ν₉⁰+ν₁₀^±1)(E)←ν₁₀^±1(E) and 3ν₉^±1(E)←ν₉^±1(E), where ν₁₀ and ν₉ are the degenerate CCC and CCH bending fundamental vibrations, respectively. Assignment of lines to the transitions of these hot bands were carried out with the help of the high-resolution spectra recorded at ∼195 K and at room temperature. Molecular parameters for these hot bands have been obtained from the rotational analysis of the partially resolved K-structure lines. Only Q-head of the third hot band , originating from the lower 2ν₁₀ state could be identified.     

Stretch-Bender Calculations of the Rovibronic Energies in the X?B1 Electronic Ground State of NH2

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the X?²B₁ state of NH₂ up to the barrier to linearity of this state. A detailed comparison has been made with experimental measurements of these rovibronic states, the majority of which are due to Vervloet and his collaborators. We have shown that, in order to fit the variation of the vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A_SO, must be increased from the earlier value of 50 cm⁻¹ of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm⁻¹. Evidence has also been provided for the large quenching of the spin-orbit coupling as the molecule bends, reflected in the large valuee of g_K=6 cm⁻¹. The pattern of calculated spinrovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally.     

The simulation of infrared bands from the analyses of rotational spectra: the 2ν9-ν9 and ν5-ν9 hot bands of HNO3

The results of millimeter and submillimeter wave rotational spectroscopy are used to simulate the complex structure of the 2ν₉-ν₉ and ν₅-ν₉ hot bands. The comparison data were obtained with a high-resolution Bruker FTIR. The combination of the quality of these data and the complexity of the spectra of these interacting states represents a stringent test for the simulation. It is shown that the agreement is very good and that this approach is generally advantageous. From this simulation, the ratios of the transition dipole moments for the 2ν₉-ν₉ and ν₅-ν₉ hot bands with respect to the ν₉ fundamental band were found to be 1.38(11) and 0.67(20), respectively. Using these results, the calculated integrated band intensities for the hot bands at were determined to be and . These results were used to successfully simulate high-resolution stratospheric spectra obtained from a balloon flight of the FIRS-2 spectrometer. The more general problem of the rotation-vibration database and the optimal use of both microwave and infrared data to define it is discussed. It is concluded that it is best if the combination of data takes place at the level of the original spectra.     

High-resolution infrared and theoretical study of the fundamental bands ν2, ν4 and ν9 and the c-Coriolis interacting dyad ν5, ν14 of 1,3,4-thiadiazole

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C₂H₂N₂S, has been recorded with a resolution of ca. 0.003 cm⁻¹ in the 800-1500 cm⁻¹ spectral region. Five fundamental bands ν₂(A₁; 1391.9 cm⁻¹), ν₄(A₁; 964.4 cm⁻¹), ν₅(A₁; 894.6 cm⁻¹), ν₉(B₁; 821.5 cm⁻¹), and ν₁₄(B₂; 898.4 cm⁻¹) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν₄ and ν₉ bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν₅ and ν₁₄ bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant . The ν₂ band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν₁₀ + ν₁₄ band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.     

H2-broadening coefficients in the ν2 and ν4 bands of PH3

H₂-broadening coefficients are measured for 41 transitions of PH₃ in the QR branch of the ν₂ band and the PP, RP, and PQ branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 2 to 16 and K from 0 to 11 are located between 995 and . The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. These coefficients γ₀(J,K) are found to decrease slightly on the whole as J increases and they decrease significantly for K values approaching or equal to J(J?4). The H₂-broadenings are also calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. The theoretical results are in satisfactory agreement with the experimental data and reproduce the J and K dependencies of the broadenings, but the decrease observed for the QR(J,K) transitions with K=J is notably overestimated.