J. Kwela

Stark effect of atomic helium second triplet series in electric fields up to 1600 kV cm−1

We present experimental and theoretical investigations of the spectral series 2 3 P‐n 3 Q (n = 3‐10, Q = S, P, D,...,n 1) in electric fields up to 1600kVcm 1 . Such fields cause—for n >6—shifts of the upper levels of the observed transitions which are larger than the separation between levels with different principal quantum numbers. The patterns belonging to a certain principal quantum number become similar to hydrogen patterns; they are nearly symmetric and show a nearly linear Stark shift in higher electric fields. The applied fields were high enough that patterns belonging to neighboring principal quantum numbers begin to overlap, which leads to interesting level-anticrossing effects. The experimental results are compared with numerical calculations taking into account mixing between states of different principal quantum numbers and also between singlet and triplet states. The agreement between experimental and theoretical line shifts is quite good.

Determination of the value of the radial integral for electric-quadrupole transitions by measurement of the relative intensity of mixed multipole lines of Bi i

The contribution of electric-quadrupole radiation to line intensity is determined by the radial integral of r2 between single electron states, s2=−e∫0∞Pnl(r)r2Pn′l′(r)dr. In this paper we give formulas for determining the value of s2 by measurements of the relative intensities of the mixed multipole transitions between levels of an ln configuration, the transitions originating from the same upper level. The formulas are used to evaluate s2 in the case of ground configuration of atomic bismuth. We find that the value of the radial integral is s2 = (9.0 ± 2.0) ea02.

Mechanical, Structural and Diffusion Studies of Hydrogel Polyurethane Nanocomposites Containing Modified Montmorillonite

Polyurethane hydrogels nanocomposites belong to a new class of hybrid biomaterials with unique swelling properties in comparison to unmodified hydrogels. These materials combine the typical properties of gels (elasticity and permeability) with the reinforcing properties of clay nanoparticles. Therefore, nanohydrogels might be applied in pharmacy for the controlled release and delivery of drugs and other biologically active agents, as well as in cosmetology as strong absorbents. We synthesized nanohydrogel polyurethanes with Cloisite® 30B organically modified clay nanoparticles of montmorillonite to obtain hybrid materials possessing great swelling properties. These materials were studied by XRD, DMA, and water absorption capacity measurements. The synthesis procedure yielded stable and homogeneous hydrogel materials. Addition of clay nanoparticles causes an increase in the absorptivity of water molecules in the polyurethane matrix.

Stark effect of atomic Helium singlet lines

We present experimental and theoretical investigations of the He spectral series 2S1−nQ1 (n=3÷9, Q=S,P,D,…,n−1) and 2P1−nQ1 (n=3÷9, Q=S,P,D,…,n−1) in electric fields up to 1635  kV/cm. Apart from the allowed transitions with |ΔL|=1, the transitions with |ΔL|=0,2,3,…—without field strictly forbidden—were observed. Several He patterns become similar to hydrogen patterns, which means they are nearly symmetric and show in higher fields nearly linear Stark shifts. The applied fields are high enough that patterns belonging to neighboring principal quantum numbers (for n>6) begin to overlap, which leads to interesting level-anticrossing effects. The experimental results are compared with numerical calculations, taking into account mixing between states of different principal quantum numbers and between singlet and triplet states. The agreement between experimental and theoretical results is quite good.

Anticrossing effects in Stark spectra of helium

In the spectral range between 480 nm and 630 nm the Stark effect of the transitions n 1Q-2 1S, n 1Q-2 1P and n 3Q-2 3P (n=3÷10, Q=S, P,...) was studied using electric field up to 1500 kV/cm. For such a high field the Stark splitting becomes greater than the simple structure of the atom. Hence anticrossings of the Stark components of the same magnetic quantum number occur. The experimental results have been compared with the theoretically determined shifts. The results of calculations show good agreement with observation.

Anisotropy in radiative decay of Ca I in an electric field

The angular distribution of the electric-field-inducedE1 radiation is asymmetric with respect to the electric field direction as a result of mixing of states of different parity. Measurement of this anisotropy in atomic calcium permits the experimental determination of the decay rate between the1P and metastable1D levels. We obtain the resultA(4s4p1P10−5s4d1D2)=(3.32±0.85±0.50)×103 s−1.

Isotope shifts in Sb I

The isotope shifts of eight lines of Sb I covering the UV–NIR spectral range have been measured. We used two different experimental techniques: high-resolution emission spectroscopy and optogalvanic absorption spectroscopy with a tunable dye ring laser system. Recurring to pseudo-relativistic Hartee–Fock estimates, the field and specific mass shifts of numerous configurations were evaluated. The comparison between experimental and ab initio line shift values is very satisfactory.

Stark effect in atomic helium in a very high electric field up to 1500 kV/cm

In the spectral range between 480 nm and 630 nm the Stark effect of the transitions n1Q-21S, n1Q-21P and n3Q-23P(n=3÷9, Q=S, P,...) was studied using electric field up to 1500 kV/cm. For such a high field the Stark splitting becomes greater than the simple structure of the atom. Hence, anticrossings of the Stark components of the same magnetic quantum number occur. The experimental results have been compared with the theoretically determined shifts. The results of caluclations show good agreement with observation not only for low field values, but also in high fields and in case of level anticrossings.

Investigation of hyperfine structure of several major lines in PbI and PbII

Hyperfine structure of several lines in neutral and singly ionized lead have been measured. The discharge tube containing metallic isotope 207Pb was used as a light source. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with CCD camera used as a detector. In the analysis of the spectra we used a computer simulation technique. Our experiment yields the following hyperfine splitting constants A: A(6p2 1D2)=(20.69 ±0.21) mK, A(6p2 3P2)=(91.37±0.34) mK A(6p7s 1P1)=(16.45±0.95) mK, A(6p7s 3P1)=(293.93±0.56) mK, A(6p6d 3F2)=(103.22±0.31) mK, A(6p6d 3F3)=(69.12±0.28) mK, A(6p8s 3P1)=(202.04±0.48) mK, A(6p8p 3P1)=(224.26±1.37) mK, A(6p8p 3D2)=(108.02±1.14) mK, A(6p7d 3D1)=(-100.86±0.53) mK for the levels of PbI and A(6s2 7s 2S1/2)=(352.1±1.7) mK, A(6s2 7p 2P3/2)=(13.6±1.3) mK, A(6s2 7p 2P1/2)=(70.8±1.1) mK for the levels of Pb II. Our results are compared with recent theory and other experiments.

Observation of the electric-field-inducedE1 transition between 5s4d1D2 and 5s21S0 levels in Sr I

The angular distribution of the electric-field-inducedE1 radiation is asymmetric with respect to the external electric field direction. Measurement of this asymmetry for the 5s4d1D2 → 5s21S0 transition in strontium permits the experimental determination of the 5s5p1P1 → 5s4d1D2 decay rate. The result is:A(1P1 →1D2)=(4.37±0.93±0.66) × 103s−1.