- Email: [email protected]
Experimental transition probabilities of infrared lines belonging to the 4p-3d transition array of Ar(I)
J. Quant. Spectrosc. Radiat. Transfer Vol. 36, No. 4, pp. 345-348, 1986 Printed in Great Britain. All rights reserved
EXPERIMENTAL INFRARED
4p-3d
0022-4073/86 $3.00+ 0.00 Copyright © 1986 Pergamon Journals Ltd
TRANSITION PROBABILITIES LINES BELONGING TO THE
TRANSITION
ARRAY
OF
O F Ar(I)
I. TANARRO a n d J. CAMPOS Catedra de Fisica Atomica Experimental, Facultad de Ciencias Fisicas, Laboratorio de Fisica Atomica, I. Basica, J.E.N. Ciudad Universitaria, 28040-Madrid, Spain (Received 27 November 1985) Abstract--Relative transition probabilities for the lines belonging to the Ar(4p-3d) transition array and coming from the six upper levels 3d (7/2) l , 3d (3/2) I , 3d (5/2)2, 3d' (5/2) 2, 3d'(3/2)2, 3d' (3/2) I (jK notation) have been determined from emission line-intensity measurements o f optically-thin light sources. Absolute transition probabilities were obtained by using the Coulomb approximation. The present results are compared with previously published theoretical and experimental data.
INTRODUCTION Until recently very few experimental studies were published on transition probabilities of lines in the infrared region of atomic spectra. This fact is mainly due to the low sensitivity of available detectors which require the use of very intense light sources and high concentrations of atoms, that may lead to undesirable self-absorption effects. By using a phase sensitive detection method, we I were able to measure, transition probabilities for the infrared lines 4p-5s of Ar and 3p-4s of Ne by employing optically thin light sources. In the present work, transition probabilities of lines belonging to six Ar(3p-4d) transition arrays have been determined. We measured emission intensities of lines arising from the same upper level to determine relative transition probabilities, whose values become independent of the upper level population when working with optically-thin light sources. Transition probabilities are given on an absolute scale by using the line-strength sum-rule 3.4and the Coulomb approximation. The results are compared with intermediate-coupling calculations of Lilly,5 who also used the Coulomb approximation, as well as with previously published experimental results of Wiese et al. 6
EXPERIMENTAL METHOD The experimental set-up used for the measurements was similar to that employed in Ref. [1]. The spectral light source was an a.c. Ar arc lamp operating at 1 A current and 1 Torr pressure. The light path was 1 cm. The spectrometer was of the Eagle type, of 1 m focal length, with a 600 grooves/mm concave grating, blazed at 9000 A. The resolution was 2 A. An infrared cut-off filter eliminated second-order radiation. The light detector was an SPb photoconductive cell (Miniwatt 61SV) cooled with dry ice. To record the spectra, a digital, phase-sensitive detector was used, with analog and digital microcomputer-compatible outputs specially designed for this type of measurements. 7 Spectral response calibration was obtained by using a black-body simulator and, independently, by using a 33-86-39-01 Bausch & Lomb tungsten strip lamp and a 33-86-25 Bausch & Lomb monochromator, which had been previously calibrated by means of a thermopile (Sensors L66). Spectral efficiencies obtained with both methods agreed well within the experimental error (10%). Although the lines studied hardly fall within regions of appreciable water absorption, water vapor in the ambient air was avoided by inserting a drying compound (Silieagel) into the spectrometer. Self-absorption tests on the Ar lines were made by placing a concave mirror behind the lamp in order to double the path length. Since no change was observed in the intensity relations, self-absorption corrections became unnecessary. 345
346
I. TANARRO and J. CAMPOS
0
o
~J
~
0
~
0
0
0
d
0
d
~
d
d
ddd
0
0
0
0
0
0
0
0
0
+I
+I
+I
+I
+I
+I
+I
+l
+1
+1
+1
eo
c
cO
+I +I
<
d d g
v/
d ~ d "~l d d d
v/
d dg
d
0
0
~
--'~ d
V/
~o~
I
•
r-~
0
0
0
~
0 ",1/
v/
v/
,
~
Q
0
2.o ~
0
~
.
O~
¢< i-,.J
0
o 0 lI
I
I
I
I
I
o m
~
0 4~
o
,
.
o
,
~
0
d Vd/ ~/1 d
V/
°
O
.
°
O
0
Experimental transition probabilities of infrared lines
~
0
0
~
0
0
~
~
0
0
~
o
d d d 4 d : ~
0
,~.
c4
{3o
c4
d4
o
o
o
g
•
•
0
0
+1
+1
+l
+1 +1 +1 0
+1 +1
~
0
o
0
•
0
o
°
.
,
ddJ~
0 cq
°
347
0
+1
+1 +1
0
~ 0
° 0
~
o 0
0
~
~
0
+1 +1 +1
0
+1
+1 +1
~ 0
(;3 •
•
.
•
•
•
•
.
o o , ~ o o ~
vl
~.//
.
.
o
~
.
o
.
•
.
.
.
0
0
0
~
0
~
.
o
~
0
0
~
v/
.
.
.
,
.
.
.
,
o
o
e
o
a
<
<
<
<
,
o
.
o
0
I
I
I
<
Io,I
I
I
<
<
<
<
348
I. TANARROand J. CAMPOS RESULTS AND DISCUSION
Transition probabilities obtained in the present work for lines belonging to the A r ( 4 p - 3 d ) transition array and coming from upper levels: 3d(7/2)1, 3d(3/2)~, 3d(5/2)2, 3d'(5/2)2, 3d'(3/2)2, 3d' (3/2)1 in j K notation are given in Table 1. Transition identifications and line wavelengths were obtained from Refs [8-10]. Relative experimental transition probabilities have been normalized to a value of 100 for the most intense line of each array with the same upper level. For unobservable, very weak lines, an upper limit is given. In order to obtain absolute transition probabilities, the line strength sum rule has been used; this rule states that, for transitions between configurations with change of the last orbital from n 1 to n ' l ' , the line-strength sum over all transitions from one level of given J to all levels of another configuration is given by Sss, = P .(2J + 1)/(21 + 1); j'
here, P is the radial part of transition probability. In applying this expression, the intensities of the lines that could not be observed have been neglected since they are supposed to be very weak. The C o u l o m b approximation has been used to determine the radial part P. Besides the radial part was calculated with wave functions obtained with the self-consistent potential of Ref. [11]. Energy values were obtained as the weighted averages of experimentally determined energies of the levels of each 3d and 4p configuration. The radial part calculated in this way was 8% smaller than that obtained with the Coulomb approximation, this estimate falls within error limits of this last approximation. Experimental errors in Table 1 are given by taking account of statistical uncertainties and the spectral calibration error. The present results are compared in Table 1 with the theoretical values of Lilly, 5 which were obtained by using the same C o u l o m b approximation and intermediate-coupling scheme. They are c o m p a r e d also with the only available experimental data of Wiese e t al., 6 obtained from a 40 A current spectral light source. As can be seen in Table 1, only small discrepancies appear between our results and those of Wiese e t al., ours being generally slightly higher than those of Ref. [6] for the most intense lines. Our results agree quite well with the theoretical values of Lilly. Thus, the present work supports these intermediate-coupling scheme calculations. Acknowledgement--This work was made with partial financial support of the Spanish CAICYT (Project 1402/82).
REFERENCES 1. I. Tanarro and J. Campos, Can. J. Phys. 63, 1389 (1985). 2. J. M. Bridges and W. L. Wiese, Phys. Rev. A 2, 285 (1970). 3. I. B. Levinson and A. A. Nikitin, Handbook for Theoretical Computation of Line Intensities in Atomic Spectra. Israel Program for Scientific Translations, Jerusalem (1965). 4. R. D. Cowan, The Theory o f Atomic Structure and Spectra. University of California Press, Los Angeles, Calif. (1981). 5. R. A. Lilly, J. opt. Soc. Am. 66, 245 (1976). 6. W. L. Wiese, J. M. Bridges, R. N. Kornblith and D. E. Kelleher, J. opt. Soc. Am. 59, 1206 (1969). 7. I. Tanarro and J. Campos, J. Phys. E: Sci. lnstrum. 19, 125 (1986). 8. A. R. Striganov and N. S. Sventitskii, Tables o f Spectral Lines of Neutral and Ionized Atoms. IFI/Plenum Press, New York (1968). 9. C. H. Humphreys, J. phys. chem. Ref. Data 2, 519 (1973). 10. S. Bashkin and J. O. Stoner Jr, Atomic Energy-Level and Grotrian Diagrams, Vol. II. North-Holland, Amsterdam (1978). 11. C. Sanchez del Rio, Introduccion a la Teoria del Atomo. Alhambra, Madrid (1977).
EXPERIMENTAL INFRARED
4p-3d
0022-4073/86 $3.00+ 0.00 Copyright © 1986 Pergamon Journals Ltd
TRANSITION PROBABILITIES LINES BELONGING TO THE
TRANSITION
ARRAY
OF
O F Ar(I)
I. TANARRO a n d J. CAMPOS Catedra de Fisica Atomica Experimental, Facultad de Ciencias Fisicas, Laboratorio de Fisica Atomica, I. Basica, J.E.N. Ciudad Universitaria, 28040-Madrid, Spain (Received 27 November 1985) Abstract--Relative transition probabilities for the lines belonging to the Ar(4p-3d) transition array and coming from the six upper levels 3d (7/2) l , 3d (3/2) I , 3d (5/2)2, 3d' (5/2) 2, 3d'(3/2)2, 3d' (3/2) I (jK notation) have been determined from emission line-intensity measurements o f optically-thin light sources. Absolute transition probabilities were obtained by using the Coulomb approximation. The present results are compared with previously published theoretical and experimental data.
INTRODUCTION Until recently very few experimental studies were published on transition probabilities of lines in the infrared region of atomic spectra. This fact is mainly due to the low sensitivity of available detectors which require the use of very intense light sources and high concentrations of atoms, that may lead to undesirable self-absorption effects. By using a phase sensitive detection method, we I were able to measure, transition probabilities for the infrared lines 4p-5s of Ar and 3p-4s of Ne by employing optically thin light sources. In the present work, transition probabilities of lines belonging to six Ar(3p-4d) transition arrays have been determined. We measured emission intensities of lines arising from the same upper level to determine relative transition probabilities, whose values become independent of the upper level population when working with optically-thin light sources. Transition probabilities are given on an absolute scale by using the line-strength sum-rule 3.4and the Coulomb approximation. The results are compared with intermediate-coupling calculations of Lilly,5 who also used the Coulomb approximation, as well as with previously published experimental results of Wiese et al. 6
EXPERIMENTAL METHOD The experimental set-up used for the measurements was similar to that employed in Ref. [1]. The spectral light source was an a.c. Ar arc lamp operating at 1 A current and 1 Torr pressure. The light path was 1 cm. The spectrometer was of the Eagle type, of 1 m focal length, with a 600 grooves/mm concave grating, blazed at 9000 A. The resolution was 2 A. An infrared cut-off filter eliminated second-order radiation. The light detector was an SPb photoconductive cell (Miniwatt 61SV) cooled with dry ice. To record the spectra, a digital, phase-sensitive detector was used, with analog and digital microcomputer-compatible outputs specially designed for this type of measurements. 7 Spectral response calibration was obtained by using a black-body simulator and, independently, by using a 33-86-39-01 Bausch & Lomb tungsten strip lamp and a 33-86-25 Bausch & Lomb monochromator, which had been previously calibrated by means of a thermopile (Sensors L66). Spectral efficiencies obtained with both methods agreed well within the experimental error (10%). Although the lines studied hardly fall within regions of appreciable water absorption, water vapor in the ambient air was avoided by inserting a drying compound (Silieagel) into the spectrometer. Self-absorption tests on the Ar lines were made by placing a concave mirror behind the lamp in order to double the path length. Since no change was observed in the intensity relations, self-absorption corrections became unnecessary. 345
346
I. TANARRO and J. CAMPOS
0
o
~J
~
0
~
0
0
0
d
0
d
~
d
d
ddd
0
0
0
0
0
0
0
0
0
+I
+I
+I
+I
+I
+I
+I
+l
+1
+1
+1
eo
c
cO
+I +I
<
d d g
v/
d ~ d "~l d d d
v/
d dg
d
0
0
~
--'~ d
V/
~o~
I
•
r-~
0
0
0
~
0 ",1/
v/
v/
,
~
Q
0
2.o ~
0
~
.
O~
¢< i-,.J
0
o 0 lI
I
I
I
I
I
o m
~
0 4~
o
,
.
o
,
~
0
d Vd/ ~/1 d
V/
°
O
.
°
O
0
Experimental transition probabilities of infrared lines
~
0
0
~
0
0
~
~
0
0
~
o
d d d 4 d : ~
0
,~.
c4
{3o
c4
d4
o
o
o
g
•
•
0
0
+1
+1
+l
+1 +1 +1 0
+1 +1
~
0
o
0
•
0
o
°
.
,
ddJ~
0 cq
°
347
0
+1
+1 +1
0
~ 0
° 0
~
o 0
0
~
~
0
+1 +1 +1
0
+1
+1 +1
~ 0
(;3 •
•
.
•
•
•
•
.
o o , ~ o o ~
vl
~.//
.
.
o
~
.
o
.
•
.
.
.
0
0
0
~
0
~
.
o
~
0
0
~
v/
.
.
.
,
.
.
.
,
o
o
e
o
a
<
<
<
<
,
o
.
o
0
I
I
I
<
Io,I
I
I
<
<
<
<
348
I. TANARROand J. CAMPOS RESULTS AND DISCUSION
Transition probabilities obtained in the present work for lines belonging to the A r ( 4 p - 3 d ) transition array and coming from upper levels: 3d(7/2)1, 3d(3/2)~, 3d(5/2)2, 3d'(5/2)2, 3d'(3/2)2, 3d' (3/2)1 in j K notation are given in Table 1. Transition identifications and line wavelengths were obtained from Refs [8-10]. Relative experimental transition probabilities have been normalized to a value of 100 for the most intense line of each array with the same upper level. For unobservable, very weak lines, an upper limit is given. In order to obtain absolute transition probabilities, the line strength sum rule has been used; this rule states that, for transitions between configurations with change of the last orbital from n 1 to n ' l ' , the line-strength sum over all transitions from one level of given J to all levels of another configuration is given by Sss, = P .(2J + 1)/(21 + 1); j'
here, P is the radial part of transition probability. In applying this expression, the intensities of the lines that could not be observed have been neglected since they are supposed to be very weak. The C o u l o m b approximation has been used to determine the radial part P. Besides the radial part was calculated with wave functions obtained with the self-consistent potential of Ref. [11]. Energy values were obtained as the weighted averages of experimentally determined energies of the levels of each 3d and 4p configuration. The radial part calculated in this way was 8% smaller than that obtained with the Coulomb approximation, this estimate falls within error limits of this last approximation. Experimental errors in Table 1 are given by taking account of statistical uncertainties and the spectral calibration error. The present results are compared in Table 1 with the theoretical values of Lilly, 5 which were obtained by using the same C o u l o m b approximation and intermediate-coupling scheme. They are c o m p a r e d also with the only available experimental data of Wiese e t al., 6 obtained from a 40 A current spectral light source. As can be seen in Table 1, only small discrepancies appear between our results and those of Wiese e t al., ours being generally slightly higher than those of Ref. [6] for the most intense lines. Our results agree quite well with the theoretical values of Lilly. Thus, the present work supports these intermediate-coupling scheme calculations. Acknowledgement--This work was made with partial financial support of the Spanish CAICYT (Project 1402/82).
REFERENCES 1. I. Tanarro and J. Campos, Can. J. Phys. 63, 1389 (1985). 2. J. M. Bridges and W. L. Wiese, Phys. Rev. A 2, 285 (1970). 3. I. B. Levinson and A. A. Nikitin, Handbook for Theoretical Computation of Line Intensities in Atomic Spectra. Israel Program for Scientific Translations, Jerusalem (1965). 4. R. D. Cowan, The Theory o f Atomic Structure and Spectra. University of California Press, Los Angeles, Calif. (1981). 5. R. A. Lilly, J. opt. Soc. Am. 66, 245 (1976). 6. W. L. Wiese, J. M. Bridges, R. N. Kornblith and D. E. Kelleher, J. opt. Soc. Am. 59, 1206 (1969). 7. I. Tanarro and J. Campos, J. Phys. E: Sci. lnstrum. 19, 125 (1986). 8. A. R. Striganov and N. S. Sventitskii, Tables o f Spectral Lines of Neutral and Ionized Atoms. IFI/Plenum Press, New York (1968). 9. C. H. Humphreys, J. phys. chem. Ref. Data 2, 519 (1973). 10. S. Bashkin and J. O. Stoner Jr, Atomic Energy-Level and Grotrian Diagrams, Vol. II. North-Holland, Amsterdam (1978). 11. C. Sanchez del Rio, Introduccion a la Teoria del Atomo. Alhambra, Madrid (1977).