- Email: [email protected]
The ionization limits of NI
Volume 27A number 2
PHYSIC S LETTERS
The inequality between W÷and W_ precludes the use of the usual relationship Ti = = (~I~E~)[E Wmn(Em to define T 1. Thus the decay of t~I(t)is not a simple exponential: its form depends on several parameters ineluding the decay scheme of the nucleus observed *~ Another consequence of VH ~kT is that W+ and W_ are no longer proportionality of W÷proportional and W. to T at to high T. The temperatures follows from the Fermi statistics of conduction electrons. At low temperatures W+ varies faster than T, approaching zero as exp(-yH/kT), while W_ varies slower than T, becoming constant for kT<< YH. The latter result
*
3 June 1968
was obtained by Cameron et al. [5]. Thus at very small kT/yHany relaxation process, however obseved, becomes temperature-independent. The abrupt change to constant shown in fig. 1 is a combined result of the inequality of W~.and W_ and of their different temperature dependences. This combined effect is stressed, because Tj becomes constant at T O.014°K, 60CoFe at O.008°K. while yH = kT for The authors would like to thank Mr. F. Bacon for assistance in performing the experiments.
References 1. N. Bloembergen and G. T. Temmer, Phys.Rev. 89 (1953) 883. 2. E. Matthias and R. J.Holliday, Phys. Rev. Letters 17 (1966) 897. 3~J. E. Templeton, D. Phil. Thesis, Oxford University (1967) J.E. Templeton and D. A. Shirely, Phys. Rev. Letters 18 (1967) 240. 4 T.Moriya, J.Phys. Soc.Japan 19 (1964) 681. 5. J.A. Cameron, I.A. Campbell, J. P. Compton and R.A.G.Lines, Phys. Letters 10(1964) 24.
Because one of the unique features of this work is the measurement of nuclear alignment parameters, it might appear that this data analysis would be simplified if the magnetization were measured instead, as in standard NMR experiments. In fact none of the above complications would be avoided thereby, nor does the assumption of a “spin temperature” materially simplify the analysis.
THE IONIZATION
LIMITS OF NI
J.W. McCONKEY and J. A. KEHNAHAN Department of Pure and Applied Physics, The Queen’s University of Belfast Received 1 March 1968
The ionization limits of N I have been calculated using the 3d - nf transitions, and found to be 117356.58 cml, 117274.25 cm-1 and 117225.35 cm—1 for the 3P 3P 2, 1 and 3P0 ground levels of NIl respectively.
A knowledge of the ionization limits of N I is of importance not only from a fundamental point of view but also because an accurate determination of the splitting of the ground configuration of the parent ion, N II, enables more reliable predictions of the wavelengths of the forbidden transitions These transitions within are this of configuration interest because to be of made. their occurrence in auroral and nebular sources. Recent measurements (1) of the wavelengths of the (3P) 3d - (3P) 6f transitions of N I have enabled the 6f levels to be accurately positioned. Eriksson (2) has previously measured the 4f and 82
.
5f levels, and so the results may be combined to enable the ionization limits to be calculated. The relevant experimental term values are given in table 1. The ionization limits were, calculated for the various sequences using the formula: 2)2 T = A - R/(n + a + b/n where A is the ionization limit and a and b are constants. R, the Rydberg constant for nitrogen, was taken as 109 733.004 cm’ (3). The results are given in table 2. The 3P 0 limit was calculated using Eriksson’s theoretical val
Volume 27A, number 2
PHYSICS
LETTERS
3 June 1968
2 2p2 (3P) nf Table energy1 levels of N I
058
2s L (K)
41 (cm~-)
51 (cm~)
F (4)
110501.72
112967.11
6f (cm~)
F (2)
110485.98
F (3)
110498.39
112965.33
114306.66
G (5)
110473.13
112953.45
114300.10
D (1)
110459.76
D (2)
110404.50
112880.50
114223.85
G (4)
110402.10
112877.88
114.222.05
G (3)
110385.30
112868.70
114216.67
D (3)
110349.11
Limit
cm1
114307.76
100
1965 I
‘
60
114301.99 3P 2 4202 ~(2)
20 D(1) 3P
c
1
05
10
15
3P
114171.95
0
F2
I I
—2C
J
______
3P
ue experimental of 112826.91 values cm-’for forthe theDD(3)(3)415fand level D (3) and61the levels. No experimental value for the D (3) 5f level is available, but due to good agreement between the theoretical and experimental values for the Sf levels (2) no significant error should result. These values compare with the single value of 117 345 cm~ given Moore [3] and a value for 3~2limit of 117by 360.95 cm-’ given by Eriksthe [4] using the series ns son with n = 3, 4, 5 and6. 2 From table 2 the splittings 3P 3P 3P2 of N II are 131.23 cm40 and 82.33 2 and cm’ respectively, with a maximum error of ± 0.5 cm’. These compare with Eriksson’s [5] values of 130.80 cm4 and 82.10 cm4 obtained from measurements on the spectrum of N II. Fig. 1 shows the relative energy values for 2s2 2p2(3P) nf and the convergence to the 3P 0,i,2 limits as n —‘ co. The energy values are given relative to the centroid of the 3p configuration, and the theoretical electrostatic (2p,nf) interaction 2 (3P)nf. Table 2 Ionization limits for 282 2p L (K)
Ionization limit (cm-1)
F (4)
117356.67
F (3)
117356.71
G(5)
117356.35
D (2)
117273.76
G (4)
117 274.28
G(3)
117274.70
Mean
1-4031
0(3)
I I -80
I
~8921 -100 6f
Sf
4f
Fig. 1. N I 2s2 2p2 (3P) nf relative energy levels.
parameter, F2, is used as abscissa [6]. The experimental and theoretical level values agree to better than 0.25 cm4 throughout.
One of the authors (J.A.K.) wishes to thank the Government of Northern Ireland, Ministry of Education, for the award of a postgraduate studentship during the course of this investigation. TheScience spectrograph usedCouncil. in our original measurethe Research ments was purchased with the aid of a grant from
N II Term
117356.58
References 1. J.W.McConkey, D.J.Burns and J.A.Kernahan, J. Quant. Spec. and Rad. Trans.. to be published. 117 274.25
3p 1
D (3) 117225.35 117225.35 3p _________________________________________________
2. 3. 4. 5. 6.
K. B. S. Eriksson. C.E.Moore, Nat. K. B. S. Eriksson. K. B.S. Eriksson, K. B. S. Eriksson,
Arkiv. Fysik 19 (1961) 235. Bur. Stand. CIRC.467 (1949). private communication. Arkiv. Fysik 13 (1958) 303. Arkiv. Fysik 19 (1961) 229.
83
PHYSIC S LETTERS
The inequality between W÷and W_ precludes the use of the usual relationship Ti = = (~I~E~)[E Wmn(Em to define T 1. Thus the decay of t~I(t)is not a simple exponential: its form depends on several parameters ineluding the decay scheme of the nucleus observed *~ Another consequence of VH ~kT is that W+ and W_ are no longer proportionality of W÷proportional and W. to T at to high T. The temperatures follows from the Fermi statistics of conduction electrons. At low temperatures W+ varies faster than T, approaching zero as exp(-yH/kT), while W_ varies slower than T, becoming constant for kT<< YH. The latter result
*
3 June 1968
was obtained by Cameron et al. [5]. Thus at very small kT/yHany relaxation process, however obseved, becomes temperature-independent. The abrupt change to constant shown in fig. 1 is a combined result of the inequality of W~.and W_ and of their different temperature dependences. This combined effect is stressed, because Tj becomes constant at T O.014°K, 60CoFe at O.008°K. while yH = kT for The authors would like to thank Mr. F. Bacon for assistance in performing the experiments.
References 1. N. Bloembergen and G. T. Temmer, Phys.Rev. 89 (1953) 883. 2. E. Matthias and R. J.Holliday, Phys. Rev. Letters 17 (1966) 897. 3~J. E. Templeton, D. Phil. Thesis, Oxford University (1967) J.E. Templeton and D. A. Shirely, Phys. Rev. Letters 18 (1967) 240. 4 T.Moriya, J.Phys. Soc.Japan 19 (1964) 681. 5. J.A. Cameron, I.A. Campbell, J. P. Compton and R.A.G.Lines, Phys. Letters 10(1964) 24.
Because one of the unique features of this work is the measurement of nuclear alignment parameters, it might appear that this data analysis would be simplified if the magnetization were measured instead, as in standard NMR experiments. In fact none of the above complications would be avoided thereby, nor does the assumption of a “spin temperature” materially simplify the analysis.
THE IONIZATION
LIMITS OF NI
J.W. McCONKEY and J. A. KEHNAHAN Department of Pure and Applied Physics, The Queen’s University of Belfast Received 1 March 1968
The ionization limits of N I have been calculated using the 3d - nf transitions, and found to be 117356.58 cml, 117274.25 cm-1 and 117225.35 cm—1 for the 3P 3P 2, 1 and 3P0 ground levels of NIl respectively.
A knowledge of the ionization limits of N I is of importance not only from a fundamental point of view but also because an accurate determination of the splitting of the ground configuration of the parent ion, N II, enables more reliable predictions of the wavelengths of the forbidden transitions These transitions within are this of configuration interest because to be of made. their occurrence in auroral and nebular sources. Recent measurements (1) of the wavelengths of the (3P) 3d - (3P) 6f transitions of N I have enabled the 6f levels to be accurately positioned. Eriksson (2) has previously measured the 4f and 82
.
5f levels, and so the results may be combined to enable the ionization limits to be calculated. The relevant experimental term values are given in table 1. The ionization limits were, calculated for the various sequences using the formula: 2)2 T = A - R/(n + a + b/n where A is the ionization limit and a and b are constants. R, the Rydberg constant for nitrogen, was taken as 109 733.004 cm’ (3). The results are given in table 2. The 3P 0 limit was calculated using Eriksson’s theoretical val
Volume 27A, number 2
PHYSICS
LETTERS
3 June 1968
2 2p2 (3P) nf Table energy1 levels of N I
058
2s L (K)
41 (cm~-)
51 (cm~)
F (4)
110501.72
112967.11
6f (cm~)
F (2)
110485.98
F (3)
110498.39
112965.33
114306.66
G (5)
110473.13
112953.45
114300.10
D (1)
110459.76
D (2)
110404.50
112880.50
114223.85
G (4)
110402.10
112877.88
114.222.05
G (3)
110385.30
112868.70
114216.67
D (3)
110349.11
Limit
cm1
114307.76
100
1965 I
‘
60
114301.99 3P 2 4202 ~(2)
20 D(1) 3P
c
1
05
10
15
3P
114171.95
0
F2
I I
—2C
J
______
3P
ue experimental of 112826.91 values cm-’for forthe theDD(3)(3)415fand level D (3) and61the levels. No experimental value for the D (3) 5f level is available, but due to good agreement between the theoretical and experimental values for the Sf levels (2) no significant error should result. These values compare with the single value of 117 345 cm~ given Moore [3] and a value for 3~2limit of 117by 360.95 cm-’ given by Eriksthe [4] using the series ns son with n = 3, 4, 5 and6. 2 From table 2 the splittings 3P 3P 3P2 of N II are 131.23 cm40 and 82.33 2 and cm’ respectively, with a maximum error of ± 0.5 cm’. These compare with Eriksson’s [5] values of 130.80 cm4 and 82.10 cm4 obtained from measurements on the spectrum of N II. Fig. 1 shows the relative energy values for 2s2 2p2(3P) nf and the convergence to the 3P 0,i,2 limits as n —‘ co. The energy values are given relative to the centroid of the 3p configuration, and the theoretical electrostatic (2p,nf) interaction 2 (3P)nf. Table 2 Ionization limits for 282 2p L (K)
Ionization limit (cm-1)
F (4)
117356.67
F (3)
117356.71
G(5)
117356.35
D (2)
117273.76
G (4)
117 274.28
G(3)
117274.70
Mean
1-4031
0(3)
I I -80
I
~8921 -100 6f
Sf
4f
Fig. 1. N I 2s2 2p2 (3P) nf relative energy levels.
parameter, F2, is used as abscissa [6]. The experimental and theoretical level values agree to better than 0.25 cm4 throughout.
One of the authors (J.A.K.) wishes to thank the Government of Northern Ireland, Ministry of Education, for the award of a postgraduate studentship during the course of this investigation. TheScience spectrograph usedCouncil. in our original measurethe Research ments was purchased with the aid of a grant from
N II Term
117356.58
References 1. J.W.McConkey, D.J.Burns and J.A.Kernahan, J. Quant. Spec. and Rad. Trans.. to be published. 117 274.25
3p 1
D (3) 117225.35 117225.35 3p _________________________________________________
2. 3. 4. 5. 6.
K. B. S. Eriksson. C.E.Moore, Nat. K. B. S. Eriksson. K. B.S. Eriksson, K. B. S. Eriksson,
Arkiv. Fysik 19 (1961) 235. Bur. Stand. CIRC.467 (1949). private communication. Arkiv. Fysik 13 (1958) 303. Arkiv. Fysik 19 (1961) 229.
83