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Submitted on 1 Jan 1985
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THE EFFECT OF ELECTRIC AND MAGNETIC
FIELDS ON THE 7F0
↔5D0 TRANSITION OF BaClF :
Sm2+ USING PHOTON-GATED HOLEBURNING
R. Macfarlane, R. Shelby, A. Winnacker
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C7, suppl6ment au nOIO, Tome 46, octobre 1985 page C7-537
THE EFFECT OF ELECTRIC AND MAGNETIC FIELDS O N THE 7 ~ o + - 5 ~ o TRANSITION OF BaClF
:
sm2+ USING PHOTON-GATED HOLEBURNINGR.M. Macfarlane, R.M. Shelby and A. Winnacker
IBM Research Laboratory, San Jose, CaZifornia 95193, U.S.A.
ABSTRACT
A new mechanism of spectral holeburning by 2-step photoionization ("photon-gated" holeburning) has recently been demonstrated. In Bac1F:!3rn2+, t h i s leads t o permanent spectral holes 25 MHz wide which we have used t o measure small linear Stark and nonlinear Zeeman coefficients of the 7 ~ 0 + + 5 ~ 0 transition of sm2+. The Zeeman coefficients agree within 4% with those calculated assuming free ion 4f6 wave functions for 7 ~ 0 and 5 ~ 0 .
INTRODUCTION
A new mechanism of spectral holeburning ("photon-gated" holeburning) has been demonstrated [ l ] in Bac1F:srn2+. This involves 2-step photoionization of sm2+ and subsequent trapping of the released electron. The resulting holes are permanent, a t least on t h e time scale of days. Stable holes of this kind can be used t o measure small frequency shifts [2] as we d o here in a high resolution (-10 MHz) study of Zeeman and Stark effects of t h e 7 ~ 0 + + 5 ~ 0 transition of t h e s m 2 + ion a t 2K. F o r these measurements, the total shifts are much less than t h e inhomogeneous linewidth and could not be measured without the use of holeburning spectroscopy. In BaClF, the sm2+ ions substitute f o r Ba2+ a t sites of C4, symmetry. [3] A n analysis of t h e emission and excitation spectrum of this material was reported by Gacon et al. [4]
J O U R N A L D E PHYSIQUE
L f I
0 1 .o 2.0
Probe Laser Frequency (GHz)
Figure 1. Nonlinear Zeeman effect of the 7 ~ 0 + * 5 ~ 0 transition of B ~ c ~ F : s ~ ~ + for H O l c using a "photon-gated" hole a s a frequency marker.
7 ~ 0 + + 5 ~ 0 NONLINEAR ZEEMAN EFFECT
Zeeman experiments were carried out in a superconducting solenoid a t fields up t o 50 kG. The field was calibrated using 19F optically detected nmr [S], and the laser scan calibration was made with a 7.5 GHz FSR optical spectrum analyzer.
A
hole was burned in the 6879A line using -1w/cm2 of cw dye laser light (width -1 MHz) for frequency selection and 10 w/cm2 of A r + laser light a t 514.5 nm for gating. Exposure times were -1 sec. Holes were detected in fluorescence excitation monitoring t h e 5 ~ 0 + + 7 ~ 2Figure 2. Plot showing the quadratic nature of the hole shift for H.
11
c (0.90 Hz/G2 and H O l c (0.77 H Z / G ~ ) .JOURNAL
DE
PHYSIQUEFigure 3. Definition of energy denominators f o r t h e perturbation calculation of nonlinear Zeeman coefficients, and a schematic diagram of the effect of magnetic and electric fields on the
'F,,A~ and 5~ A levels. For the Stark shift, t h e solid and dotted lines correspond t o opposite 0 l.
signs of the electric dipole moment.
Since A3,4 i s approximately five times larger t h a n t h e Zeeman shift arises predominantly from the depression of the groundstate due t o 7 ~ 0 - 7 ~ 1 interaction. The anisotropy of the shift comes from the 7 ~ 1 splitting which results in A2>A1 and hence a larger shift for H. l(c. There is a contribution of opposite sign from t h e excited state
5 ~ 0 - 5 ~ 1 ~ 2 interaction which produces a small but measurable effect of -0.1 H Z / G ~ . The results we obtain, and a comparison with the simple model calculation is given in Table I. The agreement is seen t o be excellent.
7 ~ 0 + + 5 ~ 0 Stark Effect
For these measurements, a crystal was sandwiched between stainless steel electrodes a t 2K, and electric fields E, up t o 40 kV/cm applied. In C4" symmetry, only E,
11
c produces level shifts and t h e observed "splittings" a r e pseudo-Stark splittings o r inequivalent shifts f o r electric dipoles parallel and antiparallel t o t h e applied field (Fig. 4). The Stark coefficients, expressed a s the shift of "up" or "down" dipoles (i.e.,one half of the hole splitting) are:
Table I1 Expt.
Figure 4. Pseudo-Stark splitting between holes in the absorption of ions with "up" and "down" electric dipoles.
C7-542 JOURNAL
DE
PHYSIQUEfor the 3 ~ 4 + + 1 ~ 2 transition of L ~ F ~ : P ~ ~ + the effect is about four times larger [6] than that reported here for sm2+. A quadratic shift is expected for B,lc but this was not observed. Calculation of Stark coefficients is difficult since they vanish for 4f6 states and arise from small admixtures of the 4f55d configuration by the noncentrosymmetric component of the crystal field. Such calculations have not been carried out.
REFERENCES
[l] Winnacker, A., Shelby, R. M. and Macfarlane, R. M., Opt. Lett.. July 1985.
[ 2 ] Volker, S. and Macfarlane, R. M., Chem. Phys. Lett.
53,
8 (1978). [3] Kiss,Z.
I. and Weakliem, H. A., Phys. Rev. Lett.15,
457 (1965).[4] Gacon, J.
