HAL Id: jpa-00218415
https://hal.archives-ouvertes.fr/jpa-00218415
Submitted on 1 Jan 1979
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
BEAM-FOIL SPECTROSCOPY OF ALUMINIUM BELOW 2000Å
J. Kernahan, E. Pinnington, K. Donnelly, J. O’Neill, R. Brooks
To cite this version:
J. Kernahan, E. Pinnington, K. Donnelly, J. O’Neill, R. Brooks. BEAM-FOIL SPECTROSCOPY OF ALUMINIUM BELOW 2000Å. Journal de Physique Colloques, 1979, 40 (C1), pp.C1-180-C1-182.
�10.1051/jphyscol:1979135�. �jpa-00218415�
JOURNAL DE PHYSIQUE Colloque C 1 , supplkment au n
"
2 , Tome 40, fkvrier 1979, page C1-180BEAM-FOIL SPECTROSCOPY OF ALUMINIUM BELOW 20002
J. A. Kernahan, E. H. Pinnington, K. E. Donnelly, J. A. O'Neill and R. L. Brooks Department of Physics, University of Alberta, Edmonton, Canada, T6G 251
~ 6 s u m 6
-
Nous nous sommes servis des transitions entre 3001 et 20001 pour une 6tude des spectres et des dur6es de vie des niveaux de A1 I1 - A1 VII.Abstract
-
We have studied spectra and mean lives of levels in A1 I1-
VII using transitions between 3008, and 20001.1.INTRODUCTION
-
During the past few years beam- foil studies of aluminium have considered the spec- tral region above 16501 [l-51 and the grazing re- gion [6,7], though recently Dumont et al. [8] have reported mean lives in A1 IV and A1 V from lines in the 11002 - 19002 range. In this paper we describe work carried out between 3101 and 20001 where we have measured mean lives for levels in A1 I1-
A1 VIIusing transitions selected from a survey of aluminium beam-foil spectra taken at energies be- tween 0.2 and 1.4 MeV.
2.EXPERIMENT
-
To accelerate a beam of Al+ ions in the 2 MV Van de Graaff generator we modified the R.F. ion source as suggested by Oona and Bickel[9].However, this failed to produce a measurable current of ~ l ' with either argon or neon as carrier gas.
We then introduced a few grams of AlC1, in an Ar atmosphere, and were able to produce beams of AIC~:,
~ 1 ~ 1 ' and ~ l ' quite easily, though in the case of
~ l + the mass 27 peak was swamped by mass 28 impur- ities (CO+ and N:) initially, as evidenced by the appearance of lines of carbon, nitrogen and oxygen
either a "Spiraltron" electron multiplier (for 3001 < X < 11001) or an E.M.R. 452G photomultiplier (for 10508, < X < 20002). Decay curves were obtained for the stronger lines by photon counting, and the data were analyzed using the program HOMER [12] to obtain the mean-life values listed in Table 1.
3.DISCUSSION OF RESULTS
-
Figure 1 shows parts of the spectrum recorded at 1.0 MeV using an ~l' beam. (We did take some spectra with an ~ 1 ~ 1 : beam at 1.0 MeV which gave an effective ~1' energy of only 275 keV.) For the higher wavelength region it can be seen that the spectrum is rich in features of A1 I11-
A1 V, but between 3001 and 7001 only two of the strong features are classified. From intensity variation with beam energy these "new"features would seem to be A1 VI or A1 VII lines.
Further work is in progress in an attempt to clas- sify them. (From various considerations we have been able to rule out impurities and/or secondorder lines.)
In Table 1, we list mean-life values obtained for various levels in A1 I1
-
VII. The quoted errors in survey spectral scans. However, prolonged run- represent one standard deviation, determined from ning of the ion source "cleaned up" the bottle, andwe obtained a pure beam of Al+ which was usable for a further 25 - 3 0 hours of ion source operation.
The main details of our experimental system for obtaining beam-foil spectra and mean lives have been reported elsewhere [lo, 111. However, the sys- tem has now been further improved by incorporating a PDP 11/05 minicomputer. This provides stepping motor control (for either the foil or wavelength drive), floppy disk data and program storage and direct interface with the main university computer for data transmission and analysis.
Spectral scans were taken at various beam ener- gies, the downstream radiation being d i s p ~ ~ s e d with a 1 metre McPherson monochromator and detected with
the probable error of the weighted mean of repeated measurements, combined with the ion velocity uncer- tainty, as discussed by Pinnington et al.. [13]. In those cases where theoretical calculations are available, we have converted our mean-life values into absorption oscillator strengths.
In A1 I1 our measurements'on the lines at 17211 and 17641, for the 3s3d D and 3p2 3 2~ mean lives respectively, give good agreement with theory, though for 17641 agreement with other experimental work is only fair. At 19901 we obtained a mean life for the 3s3d D level which is more than twice 1 as short as the previous measurement [2], but our oscillator strength agrees with the calculation of Weiss [14]. This line is one of several cascades
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979135
Figure 1. Beam-foil spectrum of aluminium at 1.0 MeV to be expected into the 3s3p 'Po upper level of the 16711 transition which we also studied. In this case our mean life gives an oscillator strength which is in reasonable agreement with theory al- though our uncertainty is rather large. However, our seven parameter fits do indicate a growing-in cascade which corresponds to the mean-life value
obtained from 19901. This is a situation where multiexponential fitting to decay data can run into difficulties
-
the primary and cascade mean lives are very similar.In A1 111, we made measurements on two members of each of the 3 s S'
-
3p 2 ~ o a n d 3p 2 ~ 0-
3d D multi- 2 plets, obtaining good agreement with previous ex- perimental work [3]. For these multiplets, several calculations of the absorption oscillator strengths are available-
with seven parameter fits our mean lives for the 3p 2 ~ 0 levels gave an oscillator strength of 0.77 ?: 0.03 which is in quite goodagree- ment with the accurate calculation of Froese-Fischer [18], and also reflected the 3d 2~ mean life by a growing-in cascade. (An ANDC analysis [20] on the 3s - 3p lines using the 3p-
3d cascades gave a n f- value of 0.87, but the analysis was not self- consistent, suggesting that other cascades should be included.) At 19361 one would expect a blend be-2 2 0
tween the 3d D
-
4f F transition in A1 111 and the 3p2 3~-
3p4s 3 ~ 0 transition in A1 11. However,if the latter lines are present, then one would also expect to observe the stronger 354s 3~ - 3p4s 3 ~ 0 multiplet around 18301. Since this was not present in our spectra we have assigned the feature at 19368 to A1 111.
In A.l IV we have made measurements using eight lines of the 3s
-
3p and 3p-
3d arrays. No theore- tical data are available, but four of the lines were studied recently by Durnont et al. [8], and in these cases we find excellent agreement with their work.In the 3p 3 ~ 0
-
3d D multiplet, our two mean-life 3 measurements gave excellent self-consistency in both the primary and cascade values. At 14471 we expect a blend between the A1 IV line and a member of the 3s' 2~-
3p' *F multiplet in A1 V. We took mean- life measurements with ion energies of 275 keV ( ~ 1 ~ 1 : at 1.0 MeV) and 1.0 MeV, our results at the two energies being different. At the higher ion energy our mean life result was in excellent agree- ment with the value w e obtained for another member of the A1 V multiplet at 14551.W e observed three transitions of the 3 s 4~ - 3 p 4 ~ 0 multiplet in A1 V and our mean-life measurements from these lines show excellent agreement with the work of Dumont et al. [8], who studied two of the
lines. For four of the remaining A1 V measurements our values confirm the other experimental work [8], while using the line at 15081 we report the first measurement of the 3p 4 ~ 0 mean life.
JOURNAL DE PHYSlQLiE
TABLE 1. Mean fives and 0bcieecLtoIt ~ l ; t l e n g h i n
Ae
11 - V 1 1 THIS EXPERIMENTOTHER EXPT.
(1)
ION TRANSITION MEAN LIFE CASCADE (ns) f-value MEAN LIFE THEORETICAL(ns) VALUES f -VALUES
1671 I1 t b
3s2 ' s - 3 ~ 3 ~ 'PO 0.72'0.11 0.6'0.1.3.520.6 1.7420.27 0.65'0. loa 1..84 ,1.85'
+Growing-in cascade. .- -- Refs. a[3],b[14],~[24],d[2],e[15],f[16],~[17],h[l9], i[18], j[5],k[21],1[8],m[22],n[23]
. . . - . . - -
-
. .-
- . . . .-
- -. -- . . . - - - Our measurements using 3101 and 3541 give the first In both cases the agreement with theory is good.experiaental mean lives for the 2s2p5 3 ~ 0 level in Mean lives obtained from strong lines that so far A1 VI and the 2szp4 4~ level in A1 VII respectively. are unclassified are available on request;
References
[ 1 1 S. Bashkln et al., J.O.S.A.
2
1395 (1967). [13] E. Pinnington et al., Can J Phys2
1961 (1974).[ 23 T. Andersen et aI., J.O.S.A.
3
1197 (1969). [14] A.W. Weiss, J. Chem. Phys.47
3573 (1967).[ 31 H. Berry et al., Phys. Scr. 1 1 8 1 (1970).
[ 41 T. Andersen et al., Phys. Scr. f! 52 (1971).
[ 51 ~ e c k s t r o m & Nysteh, Phys. Scr.
14
218 (1976).[ 6 1 J. Buchet &M. Buchet, Phys Lett
63A
267 (1977).[ 7 3 L. McIntyre, Jr. et al,, Phys Scr
11
5 (1978).[ 8 1 P. Dumont et al., Phys. Lett.
66A
472 (1978).[ 9 1 Oona & Bickel, Rev. Sci Inst
9
517 (1976).[lo] D. Irwin et al., Nucl Instr Meth
110
105 (1973).[ll] Irwin & Livingston, Can J Phys
54
805 (1976).[12] Irwin & Livingston, Comp Phys Comm
7
9 5 (1974).[15] C. Laughlin et al., ~ ~ h ~ s . J.
197
799 (1975).[16] A.W. Weiss, Aphys. J. Sup. Ser.
2
103 (1971).[17] J. Migdalek, Can. J. Phys.
3
130 (1975).[la] C. Froese Fischer, Can. J. Phys.
54
1465 (1976).[19] E. ~ i G m o n t , Physica
85C
393 (1977).[20] L.J. Curtis et al., Phys. Scr.
2
216 (1970).[21] R. McEachern et al., Can. J. Phys. 5 8 3 5 (1969).
[22] C.A. Nicolaides, Private Communication, 1972.
[23] Laughlin & Dalgarno, Phys. Rev. @ 39 (1973).
[24] P. Shorer et al., Phys. Rev. @ 1109 (1977).
