Scott E. Bisson, Earl F. Worden, John G. Conway, Brian Comaskey, John A. D. Stockdale, and Fred Nehring, "Determination of absolute transition probabilities in neutral cerium from branching ratio and lifetime measurements," J. Opt. Soc. Am. B 8, 1545-1558 (1991)
We have used the 1-m Fourier-transform spectrometer at the National Solar Observatory, Kitt Peak, Arizona, to record the emission spectrum of 140Ce from an electrodeless discharge lamp in the 4000–27 600-cm−1 range. Branching ratios are determined from the intensity data for transitions originating from common upper levels. These measurements are combined with lifetimes determined by a delayed photoionization technique to yield transition probabilities or gA values for 30 transitions. A plot of the logarithm of intensity divided by gA versus upper energy was constructed; the excitation temperature of the source was determined from this plot. Also from this plot, absolute gA values were derived for 228 of the most intense observed lines of Ce i between 10 706 and 22184 cm−1. To our knowledge, the gA values obtained here are the first reported for neutral cerium.
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Difference between observed and calculated transition frequencies. The maximum tolerable difference between the observed and calculated transition frequencies was 0.01 cm−1.
Intensities are not absolute but are relative to the source used to calibrate the FTS. Transitions to the 2437- and the 0-cm−1 levels have been corrected for self-absorption.
The integrated intensity is obtained from the expression I = 1.154 × width (10−3 cm−1) × intensity at line center (photons/s-cm−1). The factor 1.154 is from a Voigt-profile factor used in the decomp program used to fit the spectral line. Transitions to the ground and the 2437-cm−1 levels have been corrected for self-absorption. The values given in parentheses are the observed intensities.
Observed transitions from 4000 to 13784 cm−1. Of the 61 predicted transitions, 35 were in the range of observation, and 18 of these were found.
Calculated transition frequencies obtained from the energy levels of Martin et al.12
Table 2
Transition Probabilities from Branching Ratios and Delayed Photoionization Measurements of Lifetimes
Values given in parentheses are standard deviations of six measurements.
The intensity is given by 1.154 × width (10−3 cm−1) × intensity at line center (relative photons/s-cm−1). The factor 1.154 is from a Voigt-profile factor used in the decomp program to fit the spectral line. Self-absorption corrections have been applied to the strongest transitions originating from levels below 22 970 cm−1. Values given in parentheses are observed intensities and have not been corrected for self-absorption.
Percent difference of experimental gA values from calculated gA values [(Aexp − Acal)/Aexp] × 100.
Experimental gA values from Kitt Peak branching ratios and delayed photoionization measurements of lifetimes. The uncertainty of the gA values is estimated to be 12% from the combined uncertainty of the branching ratios and lifetimes.
Calculated gA values obtained from plot in Fig. 4.
These lines were blended, so gA could not be determined for these transitions.
Table 3
Transition Probabilities for 228 Strong Lines of Ce i Calculated from the Plot in Fig. 5
Energy levels from Martin et al.12
Intensity at line center (photons/s-cm−1). These values are not absolute but are relative to the source used to calibrate the FTS. All intensities have been corrected for self-absorption.
Integrated intensity is obtained from the expression I = 1.154 × intensity at line center (photons/s-cm−1) × width (10−3 cm−1). The factor 1.154 is from the Voigt profile used to fit the spectral line.
Values labeled with an asterisk were obtained directly from branching ratio and lifetime measurements. The uncertainty of the gA values is estimated to be ±15%.
Tables (3)
Table 1
Observed Transitions from the 13 784.151-cm−1 Level
Difference between observed and calculated transition frequencies. The maximum tolerable difference between the observed and calculated transition frequencies was 0.01 cm−1.
Intensities are not absolute but are relative to the source used to calibrate the FTS. Transitions to the 2437- and the 0-cm−1 levels have been corrected for self-absorption.
The integrated intensity is obtained from the expression I = 1.154 × width (10−3 cm−1) × intensity at line center (photons/s-cm−1). The factor 1.154 is from a Voigt-profile factor used in the decomp program used to fit the spectral line. Transitions to the ground and the 2437-cm−1 levels have been corrected for self-absorption. The values given in parentheses are the observed intensities.
Observed transitions from 4000 to 13784 cm−1. Of the 61 predicted transitions, 35 were in the range of observation, and 18 of these were found.
Calculated transition frequencies obtained from the energy levels of Martin et al.12
Table 2
Transition Probabilities from Branching Ratios and Delayed Photoionization Measurements of Lifetimes
Values given in parentheses are standard deviations of six measurements.
The intensity is given by 1.154 × width (10−3 cm−1) × intensity at line center (relative photons/s-cm−1). The factor 1.154 is from a Voigt-profile factor used in the decomp program to fit the spectral line. Self-absorption corrections have been applied to the strongest transitions originating from levels below 22 970 cm−1. Values given in parentheses are observed intensities and have not been corrected for self-absorption.
Percent difference of experimental gA values from calculated gA values [(Aexp − Acal)/Aexp] × 100.
Experimental gA values from Kitt Peak branching ratios and delayed photoionization measurements of lifetimes. The uncertainty of the gA values is estimated to be 12% from the combined uncertainty of the branching ratios and lifetimes.
Calculated gA values obtained from plot in Fig. 4.
These lines were blended, so gA could not be determined for these transitions.
Table 3
Transition Probabilities for 228 Strong Lines of Ce i Calculated from the Plot in Fig. 5
Energy levels from Martin et al.12
Intensity at line center (photons/s-cm−1). These values are not absolute but are relative to the source used to calibrate the FTS. All intensities have been corrected for self-absorption.
Integrated intensity is obtained from the expression I = 1.154 × intensity at line center (photons/s-cm−1) × width (10−3 cm−1). The factor 1.154 is from the Voigt profile used to fit the spectral line.
Values labeled with an asterisk were obtained directly from branching ratio and lifetime measurements. The uncertainty of the gA values is estimated to be ±15%.