Precision Measurement Method for Branching Fractions of ExcitedP1/2States Applied toCa+40 (original) (raw)
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Precision measurement of the branching fractions of the 4p 2P3/2 decay of Ca II
The European Physical Journal D, 2008
We perform precision measurements of the branching ratios of the 4p 2 P 3/2 level decay of a single 40 Ca + ion suspended in a linear Paul trap. High precision is achieved by a novel technique based on monitoring the population transfer when repeatedly pumping the ion between different internal states. The branching fractions into the 4s 2 S 1/2 , 3d 2 D 5/2 and 3d 2 D 3/2 levels are found to be 0.9347(3), 0.0587(2) and 0.00661(4), respectively. For the branching ratio A(P 3/2 −S 1/2 )/ J A(P 3/2 −DJ ) = 14.31(5), we find a forty-fold improvement in accuracy as compared to the best previous measurement.
Experimental and theoretical study of the 3d^{2}D–level lifetimes of ^{40}Ca^{+}
Physical Review A, 2005
We report measurements of the lifetimes of the 3d D 5/2 and 3d 2 D 3/2 metastable states of a single laser-cooled 40 Ca + ion in a linear Paul trap. We introduce a new measurement technique based on high-efficiency quantum state detection after coherent excitation to the D 5/2 state or incoherent shelving in the D 3/2 state, and subsequent free, unperturbed spontaneous decay. The result for the natural lifetime of the D 5/2 state of 1168(9) ms agrees excellently with the most precise published value. The lifetime of the D 3/2 state is measured with a single ion for the first time and yields 1176(11) ms which improves the statistical uncertainty of previous results by a factor of four. We compare these experimental lifetimes to high-precision ab initio all order calculations and find a very good agreement. These calculations represent an excellent test of high-precision atomic theory and will serve as a benchmark for the study of parity nonconservation in Ba + which has similar atomic structure.
The need for branching fraction measurements in multiply-charged ions
Physica Scripta, 2007
Much progress has been made in the measurement of oscillator strengths in neutral and singly-ionized atoms, providing a database for use in important applications. However, for multiply-charged ions, measured data for oscillator strengths are almost exclusively limited to low-lying unbranched transitions. Although extensive measurements of ionic lifetimes exist, the lack of branching fraction measurements in multiply-charged ions prevents these data from being converted to oscillator strengths. A significant factor leading to this deficiency involves the lack of adequate line intensity calibration standards in the vacuum ultraviolet spectral region 2000-400 Å. Here we review the interrelationships connecting these rate parameters, indicate some of the important applications for which they are needed, describe the experimental limitations that currently exist, and suggest possible methods for extending these measurements below 1000 Å.
Measurements of relative branching ratios of Λc+ decays into states containing Σ
Physics Letters B, 2002
We have studied the Cabibbo suppressed decay Λ + c → Σ + K * 0 (892) and the Cabibbo favored decays Λ + c → Σ + K + K − , Λ + c → Σ + φ and Λ + c → Ξ * 0 (Σ + K − )K + and measured their branching ratios relative to Λ + c → Σ + π + π − to be (7.8 ± 1.8 ± 1.3)%, (7.1 ± 1.1 ± 1.1)%, (8.7 ± 1.6 ± 0.6)% and (2.2 ± 0.6 ± 0.6)%, respectively. The first error is statistical and the second is systematic. We also report two 90% confidence level limits Γ(Λ + c → Σ − K + π + )/Γ(Λ + c → Σ + K * 0 (892)) < 35% and Γ(Λ + c → Σ + K + K − ) N R /Γ(Λ + c → Σ + π + π − ) < 2.8%.
2 + level densities in 40 Ca extracted from high energy-resolution (p,p′) experiments
Journal of Physics: Conference Series, 2012
The level density of 2 + states in 40 Ca has been extracted in the energy region of the isoscalar giant quadrupole resonance from a fluctuation analysis of high-energy-resolution (p, p ) data taken at incident energies of 200 MeV at the K600 magnetic spectrometer of iThemba LABS, South Africa. Quasifree-scattering cross sections were calculated to estimate their role as a background contribution to the spectra and found to be small. The shape of the background was determined from the discrete wavelet transform of the spectra using a biorthogonal wavelet function normalized at the lowest particle separation threshold. The experimental results are compared to widely used phenomenological and microscopic models.
Journal of Physical Chemistry A, 2003
Chemiluminescent reactions of hyperthermal Ca( 3 P) with CF 2 Cl 2 and CF 2 dCCl 2 were studied in a beam-gas arrangement under single collision conditions. Emissions associated with the A( 2 Π Ω ) f X( 2 Σ + ) and the B( 2 Σ + ) f X( 2 Σ + ) transitions from CaCl and CaF were observed for both reactions. The chemical and electronic branching ratios were determined for these reactions, and different results were obtained for each one. The different behavior was rationalized by a simple MO pictures. For the case of the reaction with CF 2 Cl 2 it was assumed that an electron from Ca( 3 P) is transferred to a σ*(C-Cl) orbital in CF 2 Cl 2 which, at higher translational energies can also enter into a σ*(C-F) orbital of the same molecule. In both cases the molecular anion produced is short-lived and will undergo fast decay to Clor Fto yield CaCl and CaF. For the reaction with CF 2 dCCl 2 the electron from Ca( 3 P) is transferred to a π* orbital of the reagent molecule that generates a relatively stable molecular anion with 2 Π symmetry. This anion subsequently cross over several repulsive 2 Σ surfaces associated with σ* orbitals of the C-Cl and the C-F bonds, to dissociate into Clor Fto produce CaCl and CaF. The electronic branching ratios are in good agreement with statistical distribution based on information theory approach, assuming the rigid rotor harmonic oscillator (RROH) approximation for the reaction with CF 2 Cl 2 and the formation of a collision complex for the reaction with CF 2 dCCl 2 .
Ar-supported atomic population transfer from the 3d4p 1D2 to nearby states of Ca
Chemical Physics Letters, 1997
We have investigated excitation transfers from the 3d4p ID 2 state tO the 3d4p 3F2, 4s5p 3P 2 and 4sSp 1P l states of Ca through thermal collisions with Ar following a stepwise laser excitation. The experiments were conducted in a cylindrical vapor cell containing a mixture of Ca vapor and Ar at 725°C. The transfer of population was monitored through a systematic study of fluorescence as a function of Ar pressure. The corresponding rate constants are calculated to be 1.5 × 10-~0 2.4× 10-tl and 7.4X 10-12 cm 3 s-l respectively.
Hyperfine Interactions, 1987
We describe an effective new method to measure the oscillator strengths for transitions between the excited states of atoms. The oscillator strength is determined by measuring changes in the angular distribution or polarization of fluorescence light emitted by atoms in the initial or final state of the transition of interest, after these atoms have been subject to the a.c. Stark shift of an off-resonant laser pulse. The physics of the situation is very similar to that of the conventional hook method with this difference: the roles of the atoms and the photons have been interchanged. We therefore call this new method the inverse hook method. The inverse hook method is relatively insensitive to the details of the atomic absorption lineshape and also to the temporal and spectral profile of the laser pulse. It yields absolute oscillator strengths and it is especially suitable for measurements of transitions between excited atomic states, including autoionizing states.
Lifetime measurements of first excited states in ^{16,18}C
Physical Review C, 2008
The electric quadrupole transition from the first 2 + state to the ground 0 + state in 18 C was studied through lifetime measurement by an upgraded recoil shadow method applied to inelastically scattered radioactive 18 C nuclei. The measured mean lifetime is 18.9 ± 0.9 (stat) ± 4.4 (syst) ps, corresponding to a B(E2; 2 + 1 → 0 + gs ) value of 4.3±0.2±1.0 e 2 fm 4 , or about 1.5 Weisskopf units. The mean lifetime of the first 2 + state in 16 C was remeasured to be 18.0 ± 1.6 ± 4.7 ps, about four times shorter than the value reported previously. The discrepancy between the two results was resolved by incorporating the γ-ray angular distribution measured in this work into the previous measurement.