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Submitted on 1 Jan 1979
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A SYSTEMATIC STUDY OF 2s2 2pk - 2s2pk+l - 2pk+2 TRANSITIONS IN MULTIPLY-CHARGED Cl
IONS.
J. Forester, D. Pegg, P. Griffin, G. Alton, S. Elston, H. Hayden, R. Thoe, C.
Vane, J. Wright
To cite this version:
J. Forester, D. Pegg, P. Griffin, G. Alton, S. Elston, et al.. A SYSTEMATIC STUDY OF 2s2
2pk - 2s2pk+l - 2pk+2 TRANSITIONS IN MULTIPLY-CHARGED Cl IONS.. Journal de Physique
Colloques, 1979, 40 (C1), pp.C1-208-C1-210. �10.1051/jphyscol:1979142�. �jpa-00218422�
JOURNAL DE PHYSIQUE Colloque C1, suppl&ment au n
"
2, Tome 40, fevrier 1979, page C1-208A SYSTEMATIC STUDY OF 2s2 2pk
-
2s2pk+'-
2pk*' TRANSITIONS IN MULTIPLY-CHARGED C1 IONS(*I.
J.P. Forester, D.J. Pegg, P.M. Griffin, G.D. Alton, S.B. Elston, H.C. Hayden (mm), R.S. Thoe, C.R. Vane, and J.J. Wright (Ex*)
University of Tennessee, Knoxville, Tennessee, U.S.A. and Oak Ridge National Laboratory, Tennessee, U.S.A.
Resum6. Nous avons fait une 'etude systematique des dudes de vie des niveaux bas de C1 avec de 3 5 9 electrons. La technique faisceau-lame a 5 e tilis'ee ur b mesure.
Les forces d'oscillateurs pow les transitions lrrodutype 2s5;p'
-
2s2pkPP-zpkt2
sont deduites des r6sultats.Abstract. A systematic study has been made of the radiative lifetimes of the low- lying levels of C1 ions with from 3 to 9 bound electrons. The beam-foil time of flight method was used to yak$ the meaz~rement and f values for allowed An=O transitions of the type 2s 2p
-
2s2p-
2pk+' are derived from the lifetime results.1. INTRODUCTION
Current theoretical studies of the struc- ture of many electron systems frequently involve the treatment of electron correlation contributions and relativistic corrections to the simple non-re- lativistic independent particle model. This is par- ticularly true for allowed transitions which do not involve a change in the principal quantum number i.e. An=O or in-shell processes. In the present work An=O L-shell transitions of the general type
2s22pk - 2s2pk+1 and 2s2pk+2 have been investigated for multiply charged C1 ions with from 3 to 9 bound electrons i.e. Li-like to F-like structures.
The beam-foil time-of-flight method has been used in the present work to measure the radia- tive lifetimes of the low-lying L shell levels and oscillator strengths (f values) have been derived from the results for those cases where a single channel of deexcitation exists. The f value data is valuable in the establishment of systematic trends for a particular transition along an iso- electronic sequence. The C1 ions studied here are the highest Z members of many sequences investiga- ted to date.
2. EXPERIMENT
The Oak Ridge National Laboratory model EN tandem accelerator was used to produce C1 ion beams of energies 8 , 18, 38 and 45.5 MeV in this experiment. The beam energy used in any particular measurement was chosen to efficiently produce the
desired charge state in the post-foil source. A 2.2 m grazing incidence monochromator equipped with a channel electron multiplier detector was used to disperse the foil-excited radiation emitted at approximately 90' to the beam direction. T'ne spa- tial resolution (i.e. the length of beam source recieved by the spectrometer) of the present arrangement is %0.23 mm which corresponds to a time window of %16 psec. for a 38 MeV C1 ion beam.
Most of the lifetime data presented here was ob- tained under spectral bandpass conditions of less than 0.5 A (fuihm)
.
3 . RESULTS
Figures 1 and 2 show typical intensity decay curves obtained using the standard time-of- flight procedure. The results of this experiment are summarized in Table 1. In general the results agree rather well with theory which includes both non-relativistic and relativistic calculations.
Most of the non-relativistic results have been obtained by graphically extrapolating data for ions with Z i 10. Whenever necessary multiplet f values have been calculated using average multi- plet wavelengths and assuming that the lifetime of individual levels within a term are equal (as will be the case in valid LS coupling). In most cases the uncertainties quoted on the present results ( ~ 5
-
25%) are comparable to the estimated errors on the theoretical predictions. The experimental uncertainties are arrived at in the followingArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979142
T A B L E 1
TRANSITION RATES AND f-VALUES
MR An - 0 TRANSITIONS W I T H I N THJ3 L-SlELL OF MULTIPLY-CHARGED CaORINE IONS
-
P r e s e n t Multiplet
T r a n s i t i o n
Pro b i l i t y O s c i l l a t o r S t r e n e t h s 1on
X(1)
M u l t i p l e t(
1 3 0 s - 1 ) p r e s e n t Theory(21 X I V 277.9 (2s2p)'P
-
(2p2)'s 15 0.0582
.009 0 . 0 5 2 ~ , 0 . 0 & 9 ~458.4 ( 2 ~ 2 p ) ' ~
-
(2p2)'D 1.7 0,0882
,009 0 , 0 8 2 ~ , 0.078"237.8 (2s212s
-
( 2 s 2 p ) b 0.67 0.172
.03 0 . 2 2 ~ , 0,21d, 0 . 2 0 8 ~ 2a5.5 ( 2 9 2 ~ 1 %-
(2p2)% 0.63 0.0762
,004 0 . 0 7 9 ~Ref. [2] Ref. C33 Ref. 141
a Ref. Ell Ref. [51
manner. Systematic uncertainties arising for example from the determination of the post-foil beam veloci- ty, the reproducibility of the foil position and the beam-charge normalization procedure are esti- mated to be small (~1%) at the high incident beam energies employed in the present work. Statistical uncertainties associated with the decay curve fit- ting process depend to some extent upon the inten- sity of the spectral line under study and whether or not the analysis is complicated by cascade effects bought about by the non-selective excita- tion process. A 5% uncertainty limit has been quo-
ted on the lifetimes of levels deexciting via intense transitions when cascading or blending appears not toaffect the analysis. If the line is weaker, the uncertainty limit for cascade-free transitions has been increased to 10% or more to reflect the reduced counting statistics. In more extreme cases where strong cascading or blending occurs and in cases for which the lifetime of the cascading level is comparable to that of the pri- mary level, the uncertainties can be as large as 25% or more. Large uncertainties also arise when ,lifetimes approach the lower limitoftheapparatus.
JOURNAL DE PHYSIQUE
D I S T A N C E (mm)
F i g . 1. Decay i n f l i g h t of t h e W p 3 ) 1 ~ 2 l e v e l Fig. 2. Decay i n f l i g h t of t h e (2p6)
'so
l e v e l of o f t h e C-like i o n ,c l l l +
t a k e n a t a n i n c i d e n t beam t h e 0-l?ke i o n ,c19+
t a k e n a t a n i n c i d e n t beamenergy of 38 MeV. energy of 1 8 MeV.
REFERENCES
(*) Research s u p p o r t e d by NSF, ONR, Union Carbi- C51 U . I . Safronova, A.N. Ivanova, V.N. Kharikono- d e Corp. under c o n t r a c t w i t h t h e Dept. o f va, Theor. and Expt. Chem.
2,
p . 325 (1969).Energy.
(X*) Permanent Address: U n i v e r s i t y of C o n n e c t i c u t , S t o r r s , Conn.
(Wx) Permanent a d d r e s s : U n i v e r s i t y of New Hamp- s h i r e , Durham, N.H.
[I] Y-K. Kim and J.P. Desclaux, Phys. Rev. L e t t . 36, p. 139 (1976)
-
C21 0. Sinanoglu, Nucl. I n s t r . and Meth.
110,
p . 1 9 3 (1973)
C33 L.J. Shamey, J . Opt. Soc. Am.
61,
p . 942 (1970)C41 L. Armstrong, Jr., W.R. F i e l d e r , D.L. L i n , Phys. Rev. A
