Der Zerfall von Nb94 m

Using scintillation spectrometers and coincidence techniques the decay of Nb^{94 m} has been investigated. TheK-shell conversion coefficient of the 41.5 keV isomeric transition was found to be 570±100 indicating aM 3 transition. The maximum energy of theβ-decay to the 0.87 MeV level of Mo⁹⁴ is (1.15±0.03) MeV occurring (4·5±0·7)×10^?3 per disintegration, anotherβ-decay to the 1.57 MeV level was found to be (4·0±1·3)×10^?5. From this the parities and spins of the levels involved in the decay of Nb^{94 m} are determined.     

Experimental and theoretical studies of the valence-shell dipole excitation spectrum and absolute photoabsorption cross section of hydrogen fluoride

Absolute cross sectional measurements are reported of the valence-shell dipole excitation spectrum of HF obtained from suitably calibrated high impact energy, small momentum transfer, electron energy-loss scattering intensities. Detailed assignments are provided of all prominent features observed on the basis of concomitant single- and coupled-channel RPAE calculations. The measured spectrum, obtained at an energy resolution of = 0.06 eV (fwhm) in the = 9 to 21 eV interval, includes a dissociative feature centered at = 10.35 eV assigned as X¹Σ⁺ → (1π^?14σ)A¹Π, as well as numerous strong, sharp bands in the = 13 to 16 eV excitation energy region. These bands are attributed on basis of the present calculations to Rydberg (1π^?1npπ)-valence (3σ^?14σ) mixing in X¹Σ⁺ → ¹Σ⁺ excitation symmetry, which gives rise to a long conventional progression, and to strong 1π → nsσ, moderate 1π → ndσ, and weak 1π → npσ Rydberg series in X¹Σ⁺ → ¹Π excitation symmetry. A weaker 1π → ndπ Rydberg series also contributes to the spectrum in X¹Σ⁺ → ¹Σ⁺ symmetry. The calculated and measured excitation energies and f numbers, particularly for the X¹Σ → (1π^?14σ)A¹Π, → (1π^?13pπ)B¹Σ⁺, → (1π^?13sσ)C¹Π, and → (3σ^?14σ)D¹Σ⁺ transitions, are in good quantitative accord, suggesting that the overall nature of the HF spectrum is generally clarified on basis of the present studies. Finally, tentative assignments are provided of weak features observed above the 1π^?1 ionization threshold. As in previously reported joint experimental and theoretical studies of the valence-shell spectrum of F₂, high-resolution optical VUV measurements and calculated potential energy curves aid in the assignment and clarification of the HF spectrum.     

Lasing and fluorescence properties of dye-doped xerogel

Dye-doped SiO₂-xerogels are prepared for application as laser active medium. An optical surface and a sealing of the samples are achieved by covering them with silicon oil and an optical glass window. All optical properties were compatible with the assumption that the active chromophores are dissolved in the liquid which fills the pores of the xerogel. A replacement of the dye molecules destroyed by the pumping radiation via diffusion was observed. For stilbene 3 a diffusion coefficient ofD = 0.35 × 10^–9 m²/s was determined. Thus a durable operation of the laser with low repetition rates is possible.Notation as in [10]     

Emission spectrum and formation kinetics of neon fluoride

The emission spectrum and the formation kinetics of NeF* is studied using two different excitation techniques. Bye-beam excitation of a Ne/F₂ mixture the yield was found to be low having a maximum at 0.2 hPa of F₂ and at a low neon pressure of less than 0.2 MPa. An ion exchange reaction between Ne⁺ and RbF leading to NeF* was initiated by irradiation of a mixture of neon and RbF vapor using an argon-ion beam. TheD →X transition of NeF* was observed at 107.0 nm, theB →X transition at 108.8 nm. The kinetics of the reactions are discussed.     

Resonanzstreuung am 202,8 keV-Niveau im J127

Using a gaseous Xe¹²⁷ source as exciting radiation resonance fluorescence from the 202.8 keV level in I¹²⁷ has been observed. The detection of the weak resonance effect in the presence of a strong 375 keV radiation was possible because of the high energy resolution of a Li-drifted Germanium detector. Assuming a transition energy ofQ _ECO =543 keV for the Xe¹²⁷-I¹²⁷decay the mean lifetime of the 202.8 keV level was determined to be τ=(0.56±0.09)nsec.     

Green's function calculations of ground-state correlation energies

A computationally convenient and numerically stable procedure is reported for the direct calculation of ground-state correlation energies employing one-particle Green's functions.     

Theoretical Determination of the X1Σ+g potential of Cs2 using relativistic effective core potentials

Theoretical potential energy curves are computed for the X¹Σ⁺_g state of Cs₂ using relativistic effective core potential and a large valence gaussian basis set. Eighteen electrons are correlated by a four-reference MC SCF Cl(SD) procedure. Our best calculation (with experimental values in parenthesis) gave R_e = 9.05 (8.78) bohr and D_e = 3141 (3648 ± 8) cm?1.     

The 1A1 π→π* state of formaldehyde

The ¹A₁ π→π^* state of formaldehyde is predicted to be 11.2 eV above the ground state and not diffuse.     

Spectroscopic properties of the Ar 2 * (5p) excimer states

The transitions between Ar ₂ ^* (5p) and Ar ₂ ^* (4sΣ _u) have been investigated by absorption spectrometry. The fine structure of the Ar ₂ ^* (5p ³ Π _g) was attributed to a predominantly Hund’s case a coupling. A spin orbit coupling constant of A = (9.8±0.3) cm^-1 results. Absorption by the singlet system allows one to determine the triplet/singlet splitting between the Ar ₂ ^* (4s Σ _u) states to be (540 ± 100) cm^-1. The transition probabilities of the Ar ₂ ^* (5p) and Ar ₂ ^* (6p) levels were determined by saturation spectrometry yielding values between (0.2–2.5) · 10⁶ s^-1.