He+ 2p state lifetime by a quenching-asymmetry measurement

An interference asymmetry in the angular distribution of the Ly quenching radiation emitted by He+ ions in the metastable 2s1/2 state is measured to high precision to obtain the lifetime of the 2p1/2 state. The derived lifetime of (0.997 170.000 75)×10-10 s is the most accurate available for a fundamental atomic system. A detailed discussion of systematic corrections is included. The result is in good agreement with theory, thereby confirming the theory of radiative transition probabilities to 0.075%, and indicating that differences between theory and experiment for the alkali metals must be due to either inadequate wave functions or experimental errors. © 1992 The American Physical Society

Measurement of the n=2 Lamb shift in He+ by the anisotropy method

A high-precision measurement of the 2s 2S1/22p 2P1/2 Lamb shift in He+ by the quenching-anisotropy method is reported. The theory and experimental method are described in detail. The measured value of 14042.520.16 MHz (11 parts per million) rivals the accuracy of Lamb-shift measurements in hydrogen by microwave resonance. By subtracting the known low-order terms in the Lamb shift, we interpret the results as a measurement of the order (Z)6mc2 and higher contributions to the electron self-energy GSE(Z). The various contributions to the Lamb shift are discussed, and a revised value for GSE(Z) at low Z is extracted from high-Z calculations. The theoretical value for the Lamb shift is 14042.510.2 MHz, in excellent agreement with experiment. The results provide the most sensitive available determination of GSE(Z) for low Z. Measurements and calculations for hydrogen and other members of the isoelectronic sequence are discussed. © 1991 The American Physical Society

Stark-Mixing Effect on the 6p3\text{}^{3} 2\text{}^{2}P3/2\text{}_{3}\text{}_{/}\text{}_{2} -6p3\text{}^{3} 4\text{}^{4}S3/2\text{}_{3}\text{}_{/}\text{}_{2} Transition in Bi I

The 301.5 nm electric-field-induced quench radiation on a thermal beam of neutral Bi atoms in the metastable 6p$\text{}^{3}$ $\text{}^{2}$P$\text{}_{3}\text{}_{/}\text{}_{2}$ state for transition to the ground 6p$\text{}^{3}$ $\text{}^{4}$S$\text{}_{3}\text{}_{/}\text{}_{2}$ state was observed. The measurement of the Stark-enhanced intensity of the radiation as a function of the electric field yields a relationship between the field-free-decay rates for transitions between the metastable 6p$\text{}^{3}$ $\text{}^{2}$P$\text{}_{3}\text{}_{/}\text{}_{2}$ state and the nearby states that are mixed in by the field. Using the known decay rates, the measurement sets an approximate transition rate of A(6p$\text{}^{3}$ $\text{}^{2}$P$\text{}_{3}\text{}_{/}\text{}_{2}$ → 6p$\text{}^{2}$7s $\text{}^{4}$P$\text{}_{1}\text{}_{/}\text{}_{2}$ ) ≈ (0.50 ± 0.05) s$\text{}^{-1}$

The E2 admixtures in mixed multipole lines 459.7 nm and 461.5 nm in the spectrum of Bi I

A study of the hyperfine structure of mixed M1 + E2 multipole lines 459.7 nm and 461.5 nm of Bi I are reported. The computer modelling techniques was used to obtain the predicted contour of the hyperfine structure of the lines for different values of the electric-quadrupole admixtures. By variation of free parameters describing the line shape and the electric-quadrupole admixture D, defined as the ratio of the magnetic-dipole and electric-quadrupole decay rates D=AE2/(AM1+AE2), the calculated profiles were fitted into the recorded spectra. The D values of the best fits found are (3.7 ± 0.8)% for the 459.7nm line and (7.7 ± 0.4)% for the 461.5nm. Our result is compared with recent theories and other experiments

Transition probabilities of forbidden lines in Pb I

Multiconfiguration Dirac-Fock as well as semiempirical calculations of decay rates of forbidden transitions within the ground $6s^26p^2$ configuration of neutral lead are reported and compared with relativistic Hartree-Fock results as well as with available experimental data

Intensities of helium Stark lines in the region of levels anticrossing between n = 6 and n = 7

Studies of intensities of Stark lines of atomic He have been performed. The applied fields were high enough that shifts of the upper levels of the observed transitions became larger than the separation distance between levels with different principal quantum numbers. Overlapping of structures belonging to neighboring principal quantum numbers leads to levels anticrossing effects, what is reflected in variation of intensities of the observed spectral lines. Using the density matrix theory, calculations of the line intensities have been performed. By matching the superpositions of the excited states in the theoretical calculations we can follow the results of observation. Computer simulations have been performed for the observed levels anticrossing region between n = 6 and n = 7 in the second triplet series (23P–n3Q, Q = S, P, D, ...)

Hyperfine structure and isotope shift study in singly ionized lead

Hyperfine structure and isotope shifts in five optical transitions: 424.5 nm ($6s^25f\ ^2\textrm{F}_{7/2}$–$6s^26d^2\ \textrm{D}_{5/2}$), 537.2 nm ($6s^25f\ ^2\textrm{F}_{7/2}$–$6s6p^2\ ^4\textrm{P}_{5/2}$), 554.5 nm ($6s^27d\ ^2\textrm{D}_{5/2}$–$6s^27p\ ^2\textrm{P}_{3/2}$), 560.9 nm ($6s^27p^2\ \textrm{P}_{3/2}$–$6s^27s\ ^2\textrm{S}_{1/2}$) and 666.0 nm ($6s^27p\ ^2\textrm{P}_{1/2}$–$6s^27s\ ^2\textrm{S}_{1/2}$) of Pb  II have been measured. As a light source the discharge tube was used. The hyperfine structure measurements were performed using metallic isotope 207Pb. For isotope shifts measurements natural lead 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. The hyperfine structure observations yielded the splitting constants A for seven levels of Pb II. The isotope shift studies enabled to separate the mass and the field shifts and to determine values of changes of the mean square nuclear charge radii

M1-E2 interference in the Zeeman effect of the 461.5 nm line of Bi I

Studies of the interference effect in the mixed-type forbidden line 461.5 nm are reported. A special computer program considering the M1-E2 interference was designed to obtain the predicted contour of the Zeeman structure of the line. By variation of free parameters, describing the line shape and the electric-quadrupole admixture, the calculated profiles were fitted into the recorded spectra. The E2 admixture found is (7.4± 0.4)%. Our result is compared with recent theories and other experiments