Isotope shifts and hyperfine structure in near-ultraviolet transitions of Pb I
by Doppler-free saturation spectroscopy
S. Bouazza,
1,
* D. S. Gough,
2
P. Hannaford,
2
R. M. Lowe,
2
and M. Wilson
3
1
De ´partement de Physique, Faculte ´ des Sciences, Boı ˆte Postale 1039, 51687 Reims, France
2
CSIRO Manufacturing Science and Technology, Clayton, Victoria 3169, Australia
3
Department of Physics, Royal Holloway College, University of London, Egham, Surrey TW20 OEX, United Kingdom
Received 24 July 2000; published 13 December 2000
Isotope shifts and hyperfine structures have been determined for the three near-ultraviolet transitions 405.8
nm (6 s
2
6 p
23
P
2
–6 s
2
6 p 7 s
3
P
1
o
), 368.3 nm (6 s
2
6 p
23
P
1
–6 s
2
6 p 7 s
3
P
0
o
), and 364.0 nm
(6 s
2
6 p
23
P
1
–6 s
2
6 p 7 s
3
P
1
o
) in stable isotopes of Pb I using the technique of saturated absorption spectros-
copy in a sputtered vapor. The isotope shifts for these transitions and the magnetic hyperfine interaction
constants for the 6 s
2
6 p
23
P
1,2
metastable levels are the first Doppler-free determinations for these systems
reported in the literature to our knowledge. Combined with experimental data, previously given in the litera-
ture, and pseudorelativistic Hartree-Fock estimates, the field shifts FS’s of seven relevant configurations are
deduced: FS(6 s
2
6 p 7 s ) =2461 MHz, FS(6 s
2
6 p 9 p ) =1838 MHz, FS(6 s
2
6 p 6 d ) =1820 MHz, FS(6 s
2
6 p 7 d )
=1668 MHz, FS(6 s
2
6 p 8 s ) =2132 MHz, FS(6 s
2
6 p 7 p ) =395 MHz, and FS(6 s
2
6 p 5 f ) =-461 MHz, re-
ferred to 6 s
2
6 p
2
. The hyperfine-structure integrals deduced from the experimental A factors for p electrons of
the ground configuration 6 s
2
6 p
2
are in good agreement with results of ab initio calculations.
DOI: 10.1103/PhysRevA.63.012516 PACS numbers: 31.30.Gs
I. INTRODUCTION
Hyperfine structures hfs’s and isotope shifts IS’s in
Pb I have been studied extensively over the years using clas-
sical Doppler-limited and other nonlaser techniques 1–4.
However, the only laser Doppler-free studies reported to date
to our knowledge have been for the
6 s
2
6 p
23
P
0
–6 s
2
6 p 7 s
3
P
1
o
resonance line at 283.3 nm 5.
The remaining transitions from the 6 s
2
6 p
23
P ground term
are in the near-ultraviolet or far-ultraviolet region of the
spectrum and are not easily accessible to narrow-bandwidth
cw dye lasers.
The availability of cw titanium-sapphire lasers with fre-
quency doubling has permitted high-power tens of milli-
watts narrow-bandwidth laser light to be generated in the
near ultraviolet and this has opened up an important spectral
region not easily accessible to cw dye lasers. In this paper we
report Doppler-free saturated absorption spectra for the
364.0-, 368.3-, and 405.8-nm transitions in Pb I obtained us-
ing a frequency-doubled cw titanium-sapphire ring laser. The
lead vapor is generated by cathodic sputtering in a hollow-
cathode discharge, which produces an adequate population
of the 6 s
2
6 p
23
P
1,2
metastable levels at 7819 and 10 650
cm
-1
, respectively Fig. 1. The saturated absorption spectra
permit accurate determinations of magnetic hyperfine inter-
action constants for the 6 s
2
6 p
23
P
1,2
and 6 s
2
6 p 7 s
3
P
0
o
lev-
els in
207
Pb ( I =
1
2
) and of isotope shifts for the 364.0-,
368.3-, and 405.8-nm transitions. These results represent the
first Doppler-free determinations of hyperfine structures for
the 6 s
2
6 p
23
P
1,2
metastable levels and isotope shifts for the
above transitions to our knowledge.
II. EXPERIMENT
The experimental arrangement is shown in Fig. 2. The
laser is an actively stabilized cw titanium-sapphire ring laser
Coherent 899 with an intracavity LiIO
3
frequency-doubling
crystal. The narrow-band, frequency-doubled output of this
laser is split into two counterpropagating beams, a pump
beam and a weak probe beam. The pump beam is modulated
at frequencies up to 300 kHz by an acousto-optic modulator;
*Email address: safa.bouazza@univ-reims.fr
FIG. 1. Partial energy-level scheme for Pb I showing transitions
in nanometers used in this work.
PHYSICAL REVIEW A, VOLUME 63, 012516
1050-2947/2000/631/0125167/$15.00 ©2000 The American Physical Society 63 012516-1