T. J. Wasowicz

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.

Isotope shifts in the spectrum of Pb I

Isotope shifts in twelve atomic lines of Pbu2009I: 401.9u2009nm (6p6dxa03F3→6p2 1D2), 405.8u2009nm (6p7sxa03P1→6p2 3P2), 416.9u2009nm (6p6dxa03F2→6p2 1D2), 434.0u2009nm (6p7dxa03D1→6p2 1S0),u2009 500.6u2009nm (6p7sxa01P1→6p2 1S0), 520.3u2009nm (6p8sxa03P1→6p2xa01S0), 589.6u2009nm (6p8pxa03D1→6p7su20093P0), 600.2u2009nm (6p8pxa03D2→6p7su20093P1), 601.2u2009nm (6p8pxa03D1→6p7su20093P1), 605.9u2009nm (6p8pu20093P0→6p7su20093P1), 611.0u2009nm (6p8pu20093P1→6p7su20093P0) and 723.1u2009nm (6p7su20093P1→6p2u20091D2) have been measured. As a light source the discharge tube was used. The high resolution spectral apparatus consisted of a silver coated Fabry–Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. Our studies enabled us to separate the mass and the field effects and to determine values of changes of the mean square nuclear charge radii.

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.

The E2 admixtures in mixed forbidden lines of Bi I and Pb I

The hyperfine structures (hfs) of mixed (M1+E2) multipole lines 461.5 nm (6p3 2P1/2→6p3 4S3/2) and 647.6 nm (6p3 2D5/2→6p3 4S3/2) of Bi I and 733.2 nm (6p2 1D2→6p2 3P1) of Pb I are presented. A computer modelling technique was used to obtain the predicted hfs contours of these lines. By varying the free parameters describing the line shape and the electric-quadrupole admixture DE2 the calculated profiles were fitted to the recorded spectra. The DE2 values obtained from the best fits were found to be (7.3±0.9), (17.6±1.2) and (5.0±0.6)% for the 461.5, 647.6 and 733.2 nm lines, respectively. These results are compared with other experiments and recent theories.

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.

Isotope shift study in two visible lines: 500.6 nm and 520.3 nm of Pb I

The isotope shift (IS) in two visible lines of neutral lead involving transitions 6s2 6p7s 1P1-6s2 6p2 1S0 (λ5OO.6 nm) and 6s2 6p8s 3P1-6s2 6p2 1S0 (λ520.3nm) have been measured using a Fabry-Perot interferometer. The isotope shifts between even isotopic pairs were found to be: v208-v206=73.3±0.9 mK and v208-v204=121.4±1.1 mK for 6p7s configuration and v208-v206=70.1±0.6 mK and v208-v204=135.7±0.8 mK for 6p8s configuration. The displacements of the centers of gravity of isotope 207 with respect to isotope 208 were determined to be v208-v207 CG=46.4±1.2 mK and v208-v207 CG=44.9±1.1 mK for 6p7s and 6p8s configurations, respectively.