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(6P-5D)-branching ratio in Ba II
Volume 36, number 5
OPTICS COMMUNICATIONS
1 March 1981
(6P-SD)-BRANCHING RATIO IN Ba II A. OSIPOWICZ and G. WERTH Institut fiir Physik, UniversitljtMainz, 65 Mainz, W. Germany Received 6 October 1980 Revised manuscript received 1 December 1980
Ba+ions, confined in a r.f. quadrupole trap, were laser excited into the 6Pa/s state, Observation of the decay into the metastable 5D+ and 5Ds/a states yields the branching ratio R = [1(6P3/2 - SD5/2)]/[Z(6P3/2 - 5D3/2)] = 7.58 * 0.57.
In heavy alkali-like ions the first excited P-states may decay either into the ground state or into the metastable D-states (fig. 1). The relative oscillator strength of the different decay modes are of interest for lifetime determinations of the extremely long living D-states [l] . In our experiment we suspended about lo5 Ba+ ions in a r.f. quadrupole trap [2]. The electric a.c. and d.c. fields applied to the hyperbolic shaped trap electrodes formed a potential well of 20-40 V depth. During the storage time, which usually exceeded 1 hour, the particles are essentially free of unwanted perturbations: Under UHV conditions the collision rate with background atoms was about 1 s-1 and the magnetic field was kept below 0.02 mT. We excited the ions by unpolarized resonance radiation from a broadband (10 GHz) pulsed tunable dye laser. The decay of the 6P3/, state into’the
Fig. 1. Energy diagram of Ba II.
metastable states at 614.1 and 585.3 nm resp. was detected perpendicular to the laser beam by a simple optic, consisting of a lens, interference filter and photomultiplier. The photomultiplier output was gated for 1 ps charge integrated, digitized and counted (frg. 2). The relative spectral sensitivity of our detection’system at the two different wavelength has been measured using a calibrated tungsten ribbon lamp. The overall accuracy was 4.5%. From our measured intensity ratio we calculate a branching ratio 5D5/2 and 5D3/2
R= 1(6p312 - 5D512) = 7 58 + 0 5.7 1(6P3/2 - 5D& ’ ’ .
Fig. 2. Ion trap and optkal detection system.
0 030-4018/81/0000-OOOO/% 02.50 0 North-Holland Publishing Company
359
Volume 36, number 5
OPTICS COMMUNICATIONS
The error includes the calibration uncertainty and the one standard deviation of the statistical data scattering. The obtained value is in agreement with earlier estimates by Heavens [3] (R = 9), Bucka [4] (I7 = 7), and Gallagher [5] (R = 7.7). We are indebted to Prof. R. Laabs and Mr. Hodapp of the Max Planck Institut ftir Astronomie, Heidelberg, for calibrating our detkction system. The experiment was supported by the Deutsche Forschungsgemeinschaft.
360
1 March 1981
References [l] W. Paul, 0. Osberghaus and E. Fischer, Forschungsber. Wirtschafts-u.Verkehrsministerium NordrheinWestfalen 415 (1958) 1. [ 21 F. Plumelle, M. Desaintfuscien, J.L. Duchenc and C. Audion, Optics Comm. 34 (1980) 7 1. [3] O.S. Haevens, J.Opt. Sot. Am. 51 (1961) 1058. [4] H. Bucka, J. Eichler and G. v. Oppen, 7. Naturforschung 21a (1966) 654. [5] A. Gallagher, Phys. Rev. 157 (1966) 24.
OPTICS COMMUNICATIONS
1 March 1981
(6P-SD)-BRANCHING RATIO IN Ba II A. OSIPOWICZ and G. WERTH Institut fiir Physik, UniversitljtMainz, 65 Mainz, W. Germany Received 6 October 1980 Revised manuscript received 1 December 1980
Ba+ions, confined in a r.f. quadrupole trap, were laser excited into the 6Pa/s state, Observation of the decay into the metastable 5D+ and 5Ds/a states yields the branching ratio R = [1(6P3/2 - SD5/2)]/[Z(6P3/2 - 5D3/2)] = 7.58 * 0.57.
In heavy alkali-like ions the first excited P-states may decay either into the ground state or into the metastable D-states (fig. 1). The relative oscillator strength of the different decay modes are of interest for lifetime determinations of the extremely long living D-states [l] . In our experiment we suspended about lo5 Ba+ ions in a r.f. quadrupole trap [2]. The electric a.c. and d.c. fields applied to the hyperbolic shaped trap electrodes formed a potential well of 20-40 V depth. During the storage time, which usually exceeded 1 hour, the particles are essentially free of unwanted perturbations: Under UHV conditions the collision rate with background atoms was about 1 s-1 and the magnetic field was kept below 0.02 mT. We excited the ions by unpolarized resonance radiation from a broadband (10 GHz) pulsed tunable dye laser. The decay of the 6P3/, state into’the
Fig. 1. Energy diagram of Ba II.
metastable states at 614.1 and 585.3 nm resp. was detected perpendicular to the laser beam by a simple optic, consisting of a lens, interference filter and photomultiplier. The photomultiplier output was gated for 1 ps charge integrated, digitized and counted (frg. 2). The relative spectral sensitivity of our detection’system at the two different wavelength has been measured using a calibrated tungsten ribbon lamp. The overall accuracy was 4.5%. From our measured intensity ratio we calculate a branching ratio 5D5/2 and 5D3/2
R= 1(6p312 - 5D512) = 7 58 + 0 5.7 1(6P3/2 - 5D& ’ ’ .
Fig. 2. Ion trap and optkal detection system.
0 030-4018/81/0000-OOOO/% 02.50 0 North-Holland Publishing Company
359
Volume 36, number 5
OPTICS COMMUNICATIONS
The error includes the calibration uncertainty and the one standard deviation of the statistical data scattering. The obtained value is in agreement with earlier estimates by Heavens [3] (R = 9), Bucka [4] (I7 = 7), and Gallagher [5] (R = 7.7). We are indebted to Prof. R. Laabs and Mr. Hodapp of the Max Planck Institut ftir Astronomie, Heidelberg, for calibrating our detkction system. The experiment was supported by the Deutsche Forschungsgemeinschaft.
360
1 March 1981
References [l] W. Paul, 0. Osberghaus and E. Fischer, Forschungsber. Wirtschafts-u.Verkehrsministerium NordrheinWestfalen 415 (1958) 1. [ 21 F. Plumelle, M. Desaintfuscien, J.L. Duchenc and C. Audion, Optics Comm. 34 (1980) 7 1. [3] O.S. Haevens, J.Opt. Sot. Am. 51 (1961) 1058. [4] H. Bucka, J. Eichler and G. v. Oppen, 7. Naturforschung 21a (1966) 654. [5] A. Gallagher, Phys. Rev. 157 (1966) 24.