A study of Mg iv between 80 and 2100 Å has led to the classification of 243 lines. A total of 23 odd and 64 even levels have been identified as belonging to the 2s22p5, 2s22p6, 2s2p53s, 2s22p43p, 2s22p4ns, and 2s22p4nd (n = 3, 4, 5) configurations. Matrix diagonalizations and least-squares fits to the observed levels lead to well-defined radial integrals and verify the level assignments. On the basis of comparisons in the F i isoelectronic sequence, designation changes are suggested for some 2p4(3P)3d levels of Na iii, Al v, Si vi, P vii, and S viii. New levels are given for Na iii and Al v, and some previously listed levels in Na iii and S viii are rejected as unreal. An ionization energy of 880 800 cm−1 is given for Mg iv.
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Wavelengths given to 0.001 Å have estimated uncertainties of ±0.005 Å except that 320 and 323 Å are accurate to ±0.002 Å. Those given to 0.01 Å have estimated uncertainties of ±0.01 Å.
Δν = νobs − νcalc.
The level designations are defined in Table III. The 3p and 3p′ levels are of odd parity; all others are even.
The wavelength and intensity of this line are perturbed by blending with a Mg iii line.
The wave number of this line determines the position of the upper level.
The wavelength and intensity of this line are perturbed by blending with an O v line at 760 Å in the second order.
This line is masked on some exposures by O iii 702.33 Å in the second order.
The wave number of this line determines the position of the 2s2 2p52P1/2° level.
Observed wavelengths given with two and three decimals were measured against Ti lines and have uncertainties of ±0.02 and ±0.005 Å, respectively. Those given with four decimals were measured with respect to calculated Mg iv lines. The calculated wavelengths have an absolute uncertainty of ±0.004 Å and are internally consistent to ±0.0005 Å.
The wave number is the calculated one where a calculated wavelength is given.
The level designations are defined in Table III. The 2p levels are odd parity; all others are even.
The apparent intensity and position of this line are affected by the proximity to a strong line.
The apparent intensity and position of this line are affected by the proximity to a strong line of Mg v.
Because of the mixing of the 3p2P1/2° and 2S1/2° levels, the LS names of the levels at 610 981 and 612 941 cm−1 have little meaning (see Table VII).
The 3d′ 2P1/2 and 2S1/2 levels are very mixed (see Table V).
The nd2P3/2 and 2D3/2 levels (n = 4, 5) are very mixed (see table V).
Table IV
Parameter values for the 2s2p6, 2p43s, 2p43d, 2p44s, and 2p44d configurations of Mg iv and comparison with HF values. All values are in cm−1
Parameter
Fitted value (n = 3)
Fitted/HF
Fitted value (n=4)
Fitted/HF
2s2p6
Eav
318 522±110
0.97
2p4ns
Eav
565 249±74
1.01
738 418±12
1.01
F2(2p,2p)
129 101±140
0.85
128 784±54
0.84
α(2p,2p)
1 048±8
…
1 053±5
…
G1(2p,ns)
11 649±160
1.20
2 857±34
0.99
ζ2p
1 703±30
1.05
1 835±30
1.12
2p4nd
Eav
693 277±15
1.01
784 201±25
1.01
F2(2p,2p)
129 626±40
0.84
130 669±60
0.85
α(2p,2p)
935±4
…
819±6
…
F2(2p,nd)
18 988±60
0.90
6 437±130
0.94
G1(2p,nd)
8 233±100
0.79
3 950±80
0.51
G3(2p,nd)
5 550±130
0.94
2 803±210
0.53
ζ2p
1 691±23
1.03
1 683±44
1.03
ζ3d
5.2
Fixed
…
…
Configuration interaction parameters
R1(2p2p,2snd)
−48 039±630
1.10
−39 290±440
1.41
R1(2p2p,2sns)
26 350
Fixed
15 780
Fixed
R2(2pns,2pnd)
−2 378±1000
1.82
R1(2pns,nd2p)
16 635±540
1.46
Effective parameters
D1(2p,nd)
809±64
X2(2p,nd)
−2 512±126
Mean error of least-squares level fit = 31 cm−1
(57 experimental levels)
(27 terms)
Table V
Departures from LS coupling in the 2p43d, 2p44s, and 2p44d configurations of Mg iv. Unknown levels and those with LS purities greater than 90% are omitted. Energies are given in cm−1, and ΔE is the difference between the experimental and calculated energies.
J
Expt. energy
Composition
ΔE
1/2
711 878.8
61% 3d′ 2S+36% 3d′ 2P
19
712 122.2
59% 3d′ 2P+36% 3d′ 2S
−32
3/2
680 030.88
83% 3d2D+ 9% 3d2P
19
682 469.4
86% 3d2P+10% 3d2D
−26
721 042.2
88% 4s4P+12% 4s2P
−46
723 265.1
88% 4s2P+12% 4s4P
49
767 778
70% 4d4P+16% 4d4F+ 7% 4d2D
12
769 410
52% 4d2D+34% 4d2P+6% 4d4F
17
770 947
60% 4d2P+38% 4d2D
28
5/2
676 823.77
88% 3d4F+ 8% 3d2F
10
678 392.85
75% 3d2F+11% 3d2D+10% 3d4F
−24
679 098.24
87% 3d4P+ 7% 3d2F
11
680 490.03
80% 3d2D+ 9% 3d2F+9% 3d4P
−9
768 545
58% 4d4P+19% 4d4F+13% 4d2D
−11
770 072
67% 4d2D+24% 4d2F
−21
7/2
676 072.87
80% 3d4F+20% 3d2F
−13
677 449.28
80% 3d2F+19% 3d4F
10
Table VI
Parameter values for the 2p43p configuration of Mg iv, and comparison with HF values. All values are in cm−1.
Parameter
Fitted value
Fitted/HF
Eav
622 727±19
1.01
F2(2p,2p)
128 624±190
0.83
α(2p,2p)
966 Fixed
…
F2(2p,3p)
25 747±117
1.22
G0(2p,3p)
7 361±23
0.93
G2(2p,3p)
8 602±118
1.07
ζ2p
1 699±53
1.03
ζ3p
175±53
1.13
D1(2p,3p)
2 047±93
Mean deviation of the fit = 71 cm−1
(19 experimental levels)
(9 terms)
Table VII
Departure from LS coupling in 2p43p configuration of Mg iv. Levels with LS purities greater than 95% are omitted. Energies are given in cm−1, and ΔE is the difference between the experimental and calculated energies.
Wavelengths given to 0.001 Å have estimated uncertainties of ±0.005 Å except that 320 and 323 Å are accurate to ±0.002 Å. Those given to 0.01 Å have estimated uncertainties of ±0.01 Å.
Δν = νobs − νcalc.
The level designations are defined in Table III. The 3p and 3p′ levels are of odd parity; all others are even.
The wavelength and intensity of this line are perturbed by blending with a Mg iii line.
The wave number of this line determines the position of the upper level.
The wavelength and intensity of this line are perturbed by blending with an O v line at 760 Å in the second order.
This line is masked on some exposures by O iii 702.33 Å in the second order.
The wave number of this line determines the position of the 2s2 2p52P1/2° level.
Observed wavelengths given with two and three decimals were measured against Ti lines and have uncertainties of ±0.02 and ±0.005 Å, respectively. Those given with four decimals were measured with respect to calculated Mg iv lines. The calculated wavelengths have an absolute uncertainty of ±0.004 Å and are internally consistent to ±0.0005 Å.
The wave number is the calculated one where a calculated wavelength is given.
The level designations are defined in Table III. The 2p levels are odd parity; all others are even.
The apparent intensity and position of this line are affected by the proximity to a strong line.
The apparent intensity and position of this line are affected by the proximity to a strong line of Mg v.
Because of the mixing of the 3p2P1/2° and 2S1/2° levels, the LS names of the levels at 610 981 and 612 941 cm−1 have little meaning (see Table VII).
The 3d′ 2P1/2 and 2S1/2 levels are very mixed (see Table V).
The nd2P3/2 and 2D3/2 levels (n = 4, 5) are very mixed (see table V).
Table IV
Parameter values for the 2s2p6, 2p43s, 2p43d, 2p44s, and 2p44d configurations of Mg iv and comparison with HF values. All values are in cm−1
Parameter
Fitted value (n = 3)
Fitted/HF
Fitted value (n=4)
Fitted/HF
2s2p6
Eav
318 522±110
0.97
2p4ns
Eav
565 249±74
1.01
738 418±12
1.01
F2(2p,2p)
129 101±140
0.85
128 784±54
0.84
α(2p,2p)
1 048±8
…
1 053±5
…
G1(2p,ns)
11 649±160
1.20
2 857±34
0.99
ζ2p
1 703±30
1.05
1 835±30
1.12
2p4nd
Eav
693 277±15
1.01
784 201±25
1.01
F2(2p,2p)
129 626±40
0.84
130 669±60
0.85
α(2p,2p)
935±4
…
819±6
…
F2(2p,nd)
18 988±60
0.90
6 437±130
0.94
G1(2p,nd)
8 233±100
0.79
3 950±80
0.51
G3(2p,nd)
5 550±130
0.94
2 803±210
0.53
ζ2p
1 691±23
1.03
1 683±44
1.03
ζ3d
5.2
Fixed
…
…
Configuration interaction parameters
R1(2p2p,2snd)
−48 039±630
1.10
−39 290±440
1.41
R1(2p2p,2sns)
26 350
Fixed
15 780
Fixed
R2(2pns,2pnd)
−2 378±1000
1.82
R1(2pns,nd2p)
16 635±540
1.46
Effective parameters
D1(2p,nd)
809±64
X2(2p,nd)
−2 512±126
Mean error of least-squares level fit = 31 cm−1
(57 experimental levels)
(27 terms)
Table V
Departures from LS coupling in the 2p43d, 2p44s, and 2p44d configurations of Mg iv. Unknown levels and those with LS purities greater than 90% are omitted. Energies are given in cm−1, and ΔE is the difference between the experimental and calculated energies.
J
Expt. energy
Composition
ΔE
1/2
711 878.8
61% 3d′ 2S+36% 3d′ 2P
19
712 122.2
59% 3d′ 2P+36% 3d′ 2S
−32
3/2
680 030.88
83% 3d2D+ 9% 3d2P
19
682 469.4
86% 3d2P+10% 3d2D
−26
721 042.2
88% 4s4P+12% 4s2P
−46
723 265.1
88% 4s2P+12% 4s4P
49
767 778
70% 4d4P+16% 4d4F+ 7% 4d2D
12
769 410
52% 4d2D+34% 4d2P+6% 4d4F
17
770 947
60% 4d2P+38% 4d2D
28
5/2
676 823.77
88% 3d4F+ 8% 3d2F
10
678 392.85
75% 3d2F+11% 3d2D+10% 3d4F
−24
679 098.24
87% 3d4P+ 7% 3d2F
11
680 490.03
80% 3d2D+ 9% 3d2F+9% 3d4P
−9
768 545
58% 4d4P+19% 4d4F+13% 4d2D
−11
770 072
67% 4d2D+24% 4d2F
−21
7/2
676 072.87
80% 3d4F+20% 3d2F
−13
677 449.28
80% 3d2F+19% 3d4F
10
Table VI
Parameter values for the 2p43p configuration of Mg iv, and comparison with HF values. All values are in cm−1.
Parameter
Fitted value
Fitted/HF
Eav
622 727±19
1.01
F2(2p,2p)
128 624±190
0.83
α(2p,2p)
966 Fixed
…
F2(2p,3p)
25 747±117
1.22
G0(2p,3p)
7 361±23
0.93
G2(2p,3p)
8 602±118
1.07
ζ2p
1 699±53
1.03
ζ3p
175±53
1.13
D1(2p,3p)
2 047±93
Mean deviation of the fit = 71 cm−1
(19 experimental levels)
(9 terms)
Table VII
Departure from LS coupling in 2p43p configuration of Mg iv. Levels with LS purities greater than 95% are omitted. Energies are given in cm−1, and ΔE is the difference between the experimental and calculated energies.