P.F.A. Klinkenberg

STRUCTURE AND ZEEMAN-EFFECT IN THE SPECTRUM OF THE TANTALUM ATOM Ta I

Abstract The analysis of existing wavelength data of the Ta I spectrum results in the detection of 6 ground levels and numerous higher terms, in addition to those reported by previous investigators. The total number of classified lines is now 687. They correspond to combinations between 19 even ground levels and 98 odd high levels. The Z e e m a n-effect is investigated in the region 2500–8500 A and of practically all levels the g-values can be determined. The low terms belong to the configurations 5 d 3 6 s 2 and 5 d 4 6 s ; no levels of 5 d 5 could be detected. The odd levels originate in the configurations 5 d 2 6 s 2 6 p , 5 d 3 6 s 6 p and 5 d 4 6 p , the most important multiplets of which can be identified.

The Spectrum of Trebly Ionized Thorium, Th IV

Abstract Investigations on the spectrum of the thorium spark in the infrared region result in the discovery of the 5 2 F — 6 2 D— transitions and it is proved by the Zeeman-effect that 5 2 F is the ground term of the spectrum; the doublet separation is 4325,38 cm−1. The whole visible and ultraviolet regions are examined with a view to the pole-effect in order to isolate the Th IV-lines. Subsequently the pole-effect is studied in the vacuum region down to 1540 A; below this limit down to 340 A the spectrum of the vacuum spark is measured. The existing analysis of Th IV is revised in the light of the newly obtained data.The chief outlines of the term scheme are confirmed, a few corrections introduced and a diagram of the correct terms is given. The ionization potential is 28,6 V approximately. Stress is laid on the necessity of carrying out observations below 1100 A with a lightsource of considerably lower excitation than the customary vacuum spark.

Optical isotope shifts and nuclear deformation in dysprosium

Abstract The isotope shift in six Dy I lines has been investigated by means of the technique of exchanging lightsources containing enriched isotope samples and a recording Fabry-Perot spectrometer with a digital output. The analysis of output data is made by means of an electronic computer. The results prove that the isotope shift is a mixture of mass and field effect, and that the minimum value of the specific mass effect is about 6 times the general mass effect. Assuming this minimum value as the most probable one, the relative field shift is obtained. This is interpreted as a combined volume and quadrupole shift and compared with nuclear data. The results are discussed in connection with the collective model of the nucleus taking account of nuclear deformation. A fairly consistent picture is obtained, both with respect to the irregularities in the relative field shift and the spins and parities of the odd A nuclei. The values of the nuclear deformation parameter are lower than those known from rotational level structures. Evidence is presented that the transition from the single particle model to the collective model, usually considered to take place when the 45th pair of neutrons enters, may be slightly Z -dependent so as to occur between N = 90 and N = 92 in dysprosium.

SPECTRAL STRUCTURE OF NEUTRAL AND IONIZED OSMIUM

In this paper the results of an analysis of all data available on the Os I and Os II spectra are communicated. Of a total number of 263 Os I levels 155 could be interpreted in terms of the quantum theory. The ground level system is associated with the electron configurations 5d66s2 and 5d76s, which are strongly intermingled. Of the 5d8-configuration, however, no trace has been found. In the odd system most levels could be assigned to multiplets of the configurations 5d66s6p, 5d56s26p and 5d76p. Many of the high even states have been attributed to the configurations 5d66s7s, 5d56s27s and 5d66s6d. The number of classified Os I lines is about 40% of the total number known. For the ionization potential of the Os-atom a value of (8.5 ± 0.1) V has been found. As regards Os II, the main progress in the analysis was the definite establishment of 5d56s2 6S52 and the identification of 5d56s(7S)6p 8P92, 72, 52. Approximately 15% of all known Os II lines above 2000 A have been classified. Complete tables energy levels of Os I and Os II with observed J-and g-values and quantum assignments are presented in this paper. Complete tables of classified wavelengths, observed Zeeman effects, a.s.o. have been published elsewhere.

SPECTRAL STRUCTURE OF DOUBLY AND TREBLY IONIZED HAFNIUM

Abstract A level scheme is presented which accounts for more than 80% of the observed Hf III lines. All levels in the low even group and the odd group have been given quantum assignments. The configurations involved are 5 d 2 , 5 d 6 s , 6 s 2 , 5 d 6 p and 6 s 6 p with 5 d 2 3 F 2 being the ground state of the ion. The only predicted level which could not be located, is 5 d 2 1 S 0 . Some assignments have been made also in the high even system of levels, where fragments of 5 d 7 s and 5 d 6 d have been detected. The ionization potential of Hf III is found to be 23.3 V. The fundamental levels of Hf IV have been established. They leave unexplained most of the lines attributed to that spectrum, but account for the strongest and most characteristics ones. The ionization potential derived for Hf IV is 33.3 V. The structure of the two spectra is discussed in connection with related systems.

STRUCTURE AND ZEEMAN-EFFECT IN THE SPECTRUM OF THE TANTALUM ATOM Ta I. PART II

Synopsis The analysis of the Ta I-spectrum is continued. A few ground levels and a great number of high odd levels are found in addition to those given previously. Moreover a group of high even levels is discovered from which the ionization potential is found to be (7.77 0.10) Volt. The total number of classified Ta I-lines is now 1262, corresponding to transitions between 22 even ground levels, 182 odd levels and 8 high even levels. All newly classified lines and Zeeman-effect data are presented. The interpretation of the detected energy levels is revised and extended. Configuration calculations concerning the low even levels, using the method of Racah, are helpful in locating and interpreting a number of them. Typical perturbations are pointed out.

STRUCTURE OF THE SPECTRUM OF NEUTRAL TERBIUM, Tb I

Analysis of the optical spectrum of the Tb atom by means of wavenumbers and intensities, data on selfreversal and Zeeman effect has resulted in the detection of 19 low levels of the even configuration 4ƒ85d6s2 in Tb I and hundred of odd levels with J-values from 12 to 152, and the classification of nearly 2000 observed spectral lines. In this paper the material is presented concerning the 12 even levels completing the 4ƒ85d6s28G and 8D terms (except 8G12) and 296 odd levels. The number of observed lines explained by these levels is 1366, of which 24 are doubly classified. A discussion of the term structure is given in connection with the vector model, the coupling scheme, the structure of other rare earth spectra and the results of other investigations.

On the spectra of the rare earth elements

Abstract Calculations based on well-known relations which have been derived from the vector model show a considerable difference between the multiplet separations in the configurations 4fx6s2 and 4fx−15d6s2 of some neutral rare earth spectra. They allow in some cases to conclude on the character of the ground state from only a few intervals found between most prominent lines. Applied to the case of Terbium I the ground configuration of this spectrum turns out to be 4f85d6s2. A few low levels are given. The calculations are extended to the ground terms of Tb II 4f85d6s9H and 7H and their relative positions are estimated. Empirical regularities can be interpreted in accordance with the results on Tb I. Levels of both 9H and 7H are found.

The ground state of the terbium atom

Abstract From the optical spectrum of free Tb atoms and the Zeeman effect of a few transitions it is proven that the ground state is 4f96s2 6H015/2, which is at 285.580 K below 4f85d6s2 8G13/2, the lowest state known previously.

Weak field zeeman effect observations in the spectra of Th II, Nd I and Gdi. Structure of the gd i spectrum; isotope shift of its lines

Summary Zeeman effect observations in the spectrum of Th II obtained by means of an interferometer mounting are compared with recent American high field measurements. The advantages and disadvantages of both methods are discussed. Some discrepancies between the interpretations of the detected Th II levels are pointed out. A hollow cathode light source which is more adapted to emit the neutral spectrum than an arc or the customary Back trembler, is employed for the study of spectra of the rare earth elements in low magnetic fields. A large number of Nd I splittings have been measured for the first time and confronted with a preliminary classification. For 54 excited levels g -values can be deduced. Of 300 Nd I-lines measured 50 are reported in this paper. Gd I lines show a complexity due to isotope shift, the components being resolved in 4 lines. Zeeman effect data on Gd I enable to consolidate the classification of this spectrum given by previous authors and to interpret some terms. A hitherto unknown phenomenon, consisting in a rather strong depolarization accompanied by striking intensity anomalies of the magnetic components which are usually perpendicularly polarized to the field, is observed in the light from the hollow cathode source under proper conditions. It is attributed to the electric field in the tube and therefore called electric depolarization of the Zeeman components .