JOURNAL OF THE OPTICAL SOCIETY OF AMERICA

Energy Levels and Wavelengths of the Isotopes of Mercury-199 and -200

KEiVIN BuRNsAllegheny Observatory, Pittsburgh 14, Pennsylvania

AND

KENNETH B. ADAMSWestinghouse Research Laboratory, East Pittsburgh, Pennsylvania

(Received July 3, 1952)

Electrodeless tubes containing 0.5 mg of mercury were excited by radio waves of 1 10-mc frequency.In the region 5790-2446A the wavelengths of one hundred and ten components of the complex lines inthe first spectrum of soHg"99 have been measured relative to 5460.7532A with Fabry-Perot interferometers.Thirty-five lines in the first spectrum of soHgi0° were similarly measured. Fifty energy levels of Hg-199 werederived and their centers of gravity were compared with the levels of the even isotopes. The 6s' 'So levelwas set at zero in all cases. The centers of gravity of the levels of Hg-199 fall between those of Hg-198and Hg-200 but only one-seventh as far from the former as from the latter. For eighteen well-determinedcenters the median difference between observed and interpolated is 40.002 cm-. Fourteen centers ofgravity involving twenty-nine levels of Hg-201 were derived from the data of Schuler and Keyston orSchuler and Jones. The median difference between these centers and levels interpolated between evenisotopes is 0.004 cm-'. Seven levels of Hg-204 (Schuler and Keyston, and Sterner) were compared withthe levels of the other isotopes. The 6d' D2 and 6d3 DI levels are anomalous. Two hitherto unobservedlines of the type Ip',-

3 D3 furnish levels that indicate that unlike the 3D, and D; the 3D3 levels are notinverted in the spectrum of Hg-199.

IN a manner similar to that in which mercury-198and -202 were observed,' we have observed mer-

cury-199 and -200 in the region 5790-2446A.Briefly, an electrodeless tube containing a fraction ofa milligram of mercury and 3 mm or less argon wasexcited by radio waves of 110-mc frequency. The inter-ference pattern of a Fabry and Perot interferometerwas imaged on the slit of an El Hilger quartz spectro-graph. Separators of 2 to 85 mm thickness were usedfor the region 5790 to 3125A; thicknesses of 2 to 40 mmfor 3131A and shorter. The analysis of our samplefollows.

196 0.03% 200 11.37% 202 4.25%198 7.93 201 2.36 204 0.97199 73.09

The eleven percent of Hg' 00 allowed us to observe somethirty-five lines, though only in the case of 2536.5Aand 5460.7A were the hfs components of the evenisotopes well separated. By use of samples richer in200 this spectrum can be improved and extended. Wewere compelled to observe the even isotopes in orderto distinguish between an even line and a componentof the odd. It is evident from the data of Table I thatto distinguish is not always possible. For 4339A theeven and the strongest odd component are separatedby one part in eight hundred thousand and are readilymeasurable; the weaker odd component, through nearlyas widely separated from the even, was not easilyobserved. The strongest component of 3650A consistsof two components of 199 and the three even isotopelines all in a group less than one part in a million wide.Here separation is incomplete and the wavelengthsare estimated from the broadening. In several other

I K. Bums and K. B. Adams, J. Opt. Soc. Am. 42, 56 (1952).

cases, mentioned in notes to Table I, no broadening isapparent, and the wavelengths are uncertain. The useof a richer sample of 199 will make it possible to im-prove our table at several points, and lighten greatlythe burden of untangling complex lines.

For 2536.5A the line of Hg-198 was strong enoughand well enough separated to be used as a standard.The components of Hg-199 were then somewhatoverexposed. To eliminate any effect of overexposuresome exposures were made by alternating 199 and 198every five minutes. This procedure was used for thestronger lines of the whole spectrum. When exposureshad to be long in order to photograph weak lines(5025A took two hours on a fast plate) the argon lineswere used as standards. These have been compared with5460.7532A2 in our laboratory and with 6438.4696Aby Humphreys3 at the Bureau of Standards. To obtainthe separation of the components of Hg-199 the tubeswere operated with less energy than in our earlier workand under the newer conditions argon lines show usableinterference at orders near 200,000.

In Table I the first and second columns contain,respectively, for Hg-199, the measured wavelengthsin standard air and the corresponding wave number invacuum. 4 The third column shows the fractional partof the differences of the levels indicated in column sixand found in Table II. A letter in column three indicatesthat this is the only line used to evaluate one of thelevels involved, 6d3D3-7/2 in the case of 3650A. Thefourth column contains the fractional wave number as

2W. F. Meggers and F. 0. Westfall, J. Research Natl. Bur.Standards 44, 455 (1950), RP 2091.

3 C. J. Humphreys, J. Research Natl. Bur. Stand. 20, 24 (1938),RP 1061.

4 H. Barrell, J. Opt. Soc. Am. 41, 295-299 (1951).

716

VOLUME 42, NUMBER 10 OCTOBER, 1952

ISOTOPES OF MERCURY-199 AND -200

TABLE I. Wavelengths in the spectra of mercury 199 and 200.

1 2 3 4 5Vacuum Number

wave com- 8soHgI9 No.X in air observed puted Schuler obs.

5790.8900 17263.7155790.8308 17263.8925790.6631 17264.3915790.5444 17264.745

5769.6437 17327.2875769.5994 17327.4205769.5457 17327.5815769.4863 17327.760

5460.8300 18307.1475460.7449 18307.4325460.7355 18307.4635460.5103 18308.218

5025.8248 19891.6845025.6232 19892.4825025.5211 19892.886

4916.0975 20335.6604916.0674 20335.7844916.0549 20335.836

4358.5176 22937.1334358.3804 22937.8554358.4313 22938.1134358.3160 22938.1944358.1762 22938.930

4347.5774 22994.8514347.5444 22995.0254347.4964 22995.2804347.4498 22995.526

4339.2304 23039.0834339.2250 23039.1124339.220C 23039.---4339.1871 23039.309

4108.0772 24335.4214108.0573 24335.5384108.0476 24335.596

4077.8785 24515.6334077.8343 24515.8984077.7553 24516.373

4046.6878 24704.5884046.5676 24705.3224046.5120 24705.661

3906.4280 25591.5833906.3717 25591.9523906.3426 25592.143

3901.8670 25621.4973901.867C 25621.---

3801.6796 26296.6963801.661- 26296.8253801.6538 26296.875

3704.1451 26989.1013704.170M 26988.---

3701.434- 27008.869

3.7153.8954.3904.745

7.2897.4197.5867.766

7.1397.4327.4618.208

1.6842.4782.880

5.6565.7825.836

7.1267.8628.1188.1948.930

4.8485.0285.2835.534

9.0769.1149.1489.328

5.418S

5.598

5.635S

6.371

4.5955.3275.663

1.592D

2.16-

1.4971.495

6.696S

6.876

D8.916

8.864

3.711 183.892 3

104.752 26

7.288 2918

7.581 257.758 3

7.148 226

7.463 48.216 9

5_6_8 11

__ _ 1

5.658 1011

5.839 7

7.136 47.851 14

148.197 248.927 5

4.851 225.032 3

95.528 30

76C1

5.413 71

5.594 10

5.636 179

6.369 14

4.583 188

5.656 25

819

__ _ 1

C

__ _ 112

3M

33701.436C 27008.--- 8.854

6

Levelcombinations

1/2-3/23/2-3/2

6p 'P 1 - 6d 1D23/2-5/2

3/2-5/26p P 1- 6d 3D2

1/2-3/23/2-3/2

3/2-1/26p 3P 0

2 - 7s 3S5/2-3/23/2-3/2

1/2-1/26p 'Po- 8s 3S

3/2-3/2

1/2-1/26p PI- 8s So

3/2-1/2

3/2-1/21/2-1/2

6p 3P 1- 7s S,3/2-3/21/2-3/2

1/2-3/23/2-3/2

6p 'PI- 7d 'D23/2-5/2

3/2-5/26p 'P0 - 7d 3D2

1/2-3/23/2-3/2

1/2-1/26p 'P0 - 9s 'So

3/2-1/2

3/2-1/26p 3Ps- 7s So

1/2-1/2

1/2-1/26p 3Po- 7s 3S1

1/2-3/2

1/2-3/26p 1P 1- 8d 'D2

3/2-5/2

3/2-5/26p TP 1- 8d 3D2

1/2-1/26P 'P0 - lOs'So

3/2-1/2

3/2-5/26p 'P0 - 9d 1D 2

3/2-5/2C 6P 1P 0

1 -9d D2

1 2Vacuum

waveX in air observed

3663.397C 27289.---3663.2961 27290.0463663.282C 27290.---3663.280C 27290.---3663.182C 27290.---

3662.9295 27292.7773662.879C 27293.---3662.829C 27293.---3662.779C 27293.---

3654.9069 27352.6873654.842C 27353.---3654.8387 27353.1943654.8051 27353.4483654.7416 27353.923

3650.2544 27387.5453650.1549 27388.2923650.1530* 27388.306

3341.5070* 29918.0123341.4795 29918.2573341.477C 29918.---3341.393C 29919.---

3131.921C 31920.---3131.8487 31920.7673131.840C 31920.---3131.8390 31920.866

3131.5804 31923.5023131.547C 31923.---3131.543C 31923.---3131.507C 31924.---3131.4714 31924.613

3125.7131 31983.4243125.6686 31983.8813125.666C 31983.---3125.5944 31984.638

3122.3107* 32018.274

3027.546C 33020.---3027.4990 33020.9443027.4882 33021.0633027.4770 33021.1553027.431C 33021.---

3025.6500 33041.1233025.6070 33041.5953025.584- 33041.8443025.5358 33042.370

3023.5132 33064.4733023.490C 33064.---3023.475C 33064.---3023.444C 33065.---3023.422C 33065.---

3021.5658 33085.7823021.499C 33086.---3021.4972* 33086.5353021.4972 33086.535

3. 4 5Number

com- soHg'99 No.puted Schuler obs.

9.2950.0430.1470.1660.893

2.7773.15-3.5233.900

2.6913.1683.1953.4373.914

7.543DD

8.0138.2548.2829.028

0.0300.7660.8520.880

3.5103.84-3.8874.2464.623

3.4243.8813.9014.637

8.276

0.4300.9361.0591.1761.682

1.1251.5931.8712.373

4.4784.7304.8905.2245.476

5.7726.518DD

6

Levelcombinations

C 5/2-3/29 3/2-3/2

C 5/2-5/2C 6p 3

P° 2 -6d 'D2C 3/2-5/2

1 5/2-3/2C 6p 3P 2 -6d 3 DC 3/2-3/2C 3/2-1/2

2.693 16 5/2-5/2---- C 5/2-3/2

9 6p 3P° 2 -6d

3D23.451 3 3/2-5/23.921 7 3/2-3/2

---- 15 5/2-5/24 6p 3P° 2 -6d 3D3

---- 5 5/2-7/2

8.043 2 3/2-1/21 6P 3

P°2-8s 3S

8.341 C 5/2-3/29.080 C 3/2-3/2

---- C 3/2-3/21 1/2-3/2C 6p 3Pi 1 -6d D22 3/2-5/2

2 3/2-3/2C 6p 3P0

1-6d 3 DC 3/2-1/2C 1/2-3/21 1/2-1/2

3.437 12 3/2-5/24 6p 3P0

5-6d 3D2---- C 3/2-3/24.639 16 1/2-3/2

---- 8 3/2-5/26p 3 P, 1 -6d 3D3

C 5/2-3/211 5/2-5/26 6p 3P°2 -7d 'D28 3/2-3/2C 3/2-5/2

7 5/2-3/25 6p 3P° 2 -7d 3 D2 3/2-3/23 3/2-1/2

17 5/2-5/2C 5/2-3/2C 6P 3

P° 2 -7d 3D2

C 3/2-5/2C 3/2-3/2

8 5/2-5/2C 3/2-5/2

---- 26 5/2-7/226 6p 3 P°2 -7d 3D3

October 1952 717

K. BURNS AND K. B. ADAMS

TABLE I.-(Continited).

1 2Vacuum

waveX in air observed

2967.28662967.28152967.2534

33690.97933691.03833691.356

2967.5954* 33687.473

2925.43322925.41162925.410C*2925.3459

2893.67522893.61402893.59652893.58982893.5280

2856.95842856.93792856.8990

2806.775-*2806.763C2806.749-

2805.388-2805.347C

2804.46832804.43722804.3998

2803.469M2803.4686

2759.72622759.708C

2759.7074

2752.83232752.78182752.7562

2699.40092699.37522699.3406

2698.830M2698.827-2674.92982674.916M2674.9136*

34172.96534173.21834173.---34173.985

34547.99534548.72634548.93934549.01534549.752

34991.97434992.22534992.702

35617.58235617.---35617.905

35635.18935635.---

35646.87235647.26735647.743

35659.---35659.583

36224.76736225.---

36225.014

36315.48136316.14636316.484

37034.26237034.61437035.089

37042.---37042.14-37373.04437373.---37373.270

3Number

com-puted

0.9771.05-D

7.499

2.9463.2103.2343.980

8.0008.7368.9409.0159.751

1.971S

2.707

7.57-7.7257.920

5.2315.707

6.8997.2717.772

9.575

4.7605.00-

5.023

5.4696.1496.484

4.273DD

2.090DS

3.24-S

4

ssHg'99Schuler

5 6

No. Levelobs. combinations

1 1/2-3/21 6p 3

P0O-6d

3Ds

___- 10 1/2-1/2

4 1/2-3/26p 3 P0O-6d 5D2

---- 12 3/2-1/214 6p 3

PI 2 -9s IS5

C 5/2-3/27 3/2-3/2

7.973 3 3/2-1/28.724 18 1/2-1/2

3 6p 3 P0I-8s IS,

9.008 3 3/2-3/29.751 3 1/2-3/2

---- 11 3/2-1/211 6p 3P°s-8s 'So5 1/2-1/2

6 5/2-5/2C 6p 3P2-8d D24 3/2-3/2

2 5/2-3/2C 6p 3P0

2 -8d 3Ds

9 5/2-5/26 6p 3

P%2-8d 3D2

3 3/2-3/2

M 6p 3 P2-8d 3D3

---- 22 5/2-7/2

9 3/2-1/2C 5/2-3/2

8 6p 3P°2-1s

3SS

5.439 10 1/2-1/219 6P 3 P°o-8s S1

6.490 34 1/2-3/2

---- 6 5/2-5/23 6p

3P 2 -9d

3D2

4 3/2-3/2

M____ 6____ 4

M-- 4

6p 3P02 -9d 3D3

5/2-7/23/2-1/2

6p 3P02 -1 ls 3S

5/2-3/2

3650 This component and the even line were not resolved; the valueswere estimated from the broadening of the line.

3341 We never obtained the proper exposure and interferometer thicknessfor this line. The levels are very well established and the computednumbers should be accurate. No reason could be found for the dis-agreement with Schuler and Jones (see reference 6).

3122 This level combination is not found in the spectra of the evenisotopes. The line makes possible the identification of the 6d

3D3

components which have nearly the same separation as the com-bining 6p 3P°2.3021 The strongest component of 199 and the even line fall together andshow 110 broadening with an order of 264,000. The levels deducedon the assumption of exact coincidence are- n agreement with inter-polated values.

2967.5 This combination is not found in the spectra of the even isotopes.Our observations are uncertain because of the neighboring strongline but our computed value agrees exactly with that published byKessler (Phys. Rev. 77, 559 (1950)).

1 2Vacuum

waveX in air observed

2655.17002655.1324*2655.129C2655.1173

2653.71122653.68132653.670C2653.65942653.6238

2652.06752652.04132651.9973

2650.5701*

2639.7830*2639.787M

2576.35452576.30222576.289C2576.28522576.2349

2536.53902635.51622536.4919

2534.77702534.76822534.7456

2483.82512483.820C2483.8055

2482.73652482.71032482.6922

2482.01722481.99832481.9634

2464.10672464.06332464.0432

2446.91052446.897C2446.8961

37651.15837651.69137651.---37651.905

37671.85437672.27937672.---37672.58937673.095

37695.20137695.57337696.199

37716.495

37870.60937870.---

38802.90638803.69638803.---38803.95038804.707

39411.94739412.30139412.679

39439.34039439.47939439.833

40248.33340248.---40248.651

40265.98140266.40640266.699

40277.65040277.95740278.523

40570.38640571.10140571.432

40855.47540855.---40855.715

3Number

com-puted

1.1631.6691.7451.899

1.8582.2792.3602.5943.096

5.2115.573

D

6.505

D0.55-

2.9333.6693.8963.9674.703

SSS

9.3279.4869.829

8.32-8.4068.643

5.9646.4026.700

7.6327.9578.495

0.4021.1051.436

5.4835.6955.73-

4

soHg9 9

Schuler

5

No.obs.

5___- 13

C____ 16

____ 1910C39

---- 2269

3

____ 13M

37C

---- 22___- 1

1.966 1410

2.693 14

---- 126

____ 18

9C6

____ 14124

---- 2024

---- 12

91012

7C

____ 12

6

Levelcombinations

3/2-3/23/2 - 5/2

6p 3P0,-7d 'D2

1/2-3/2

3/2-3/26p 3P0

1 -7d 3D3/2-1/21/2-3/21/2-1/2

3/2-5/26p 3PI,-7d 3D2

1/2-3/2

3/2-5/26p 3P0

1-7d 3D3

5/2-7/26p 3P 2 -10d 3D3

3/2-1/21/2-1/2

6p 3P 05-9s Si

3/2-3/21/2-3/2

1/2-1/26s

25O -6p 3PI,

1/2-3/2

1/2-3/26p 3P0o-7d 3D3

1/2-1/2

3/2-5/26p 3

P0

5-8d 'D2

1/2-3/2

3/2-3/26p 3P0

5-8d 3D,1/2-3/2

3/2-5/26p 3P°, -8d 3D2

1/2-3/2

1/2-1/26p 3PIs-9s S,

1/2-3/2

1/2-1/26p 3P 5 lJOs 3S

3/2-3/2

2925 The strong component of 199 and the line of 200 are as nearly incoincidence as can be determined from our plates.

2806 Like 2925.2803 Like 2925.2759 Like 2925.2674 Like 2925.2655 Like 2925.2650 This level combination is not found in the spectra of the even iso-

topes. This line makes possible the identification of the 7d 3D3 levels

which have nearly the same separation as the combining 6p 3P°2.2639 Like 2925.2576 Like 2925.2536 The data of Schuler and Keyston (see reference 5) are influenced

by the presence of components of the 201 line.2446 Like 2925.

Vol. 42718

ISOTOPES OF MERCURY-199 AND -200

TABLE II. Even levels of 8omercury' 5 5 .

Wavenumber

00000.00063928.31674404.65278404.41480365.69-

62349.80762350.87573960.68073961.69678215.61478216.64880267.42880268.41-

71332.71171333.56177063.84477064.35079660.58879660.98-

81057.917a

71336.56871336.18971396.58271396.10571430.95771431.720'77085.04177084.53977108.144a77107.89277129.18677129.945a

79678.64579690.44079690.31379702.24-79703.03-a

81077.757a81077.687

a Only one line was available for the determination of t

TABLE Ila. Odd levels of somercury9'"

6p 3P0 -1/2 37645.2136p 3P0 i-1/2 39411.9456p 'P' 1 -3/2 39412.6816p 3P0

2 -3/2 44042.6686p 3P 2-5/2 44043.414

6p 'P01 -1/2 54068.996

6p 1P 0 1-3/2 54068.816

8p 3P°-3/2 76823.129,8p 3P0

2 -5/2 76823.955,

8p 1P01 -1/2 78813.199

8p 1P01 -3/2 78813.030

9p Pip-1/2 79964.1769p 'P0 t-3/2 79963.787

Center ofgravity

62350.519

73961.357

78216.303

80268.08-

71333.221

77064.148

79660.82-

71336.315

71396.296

71431.393

77084.706

Level

6S2 iSO

7s 'So8s 'So9s 'So

7s 'Si8s 'i9s S,

Os S,I s 3S

6d D27d D28d 1D29d D2

TABLE III. Even levels of 8omercurym.

Wavenumber

00000.00063928.202,74404.545a78404.301

62350.41973961.24178216.1978 0 2 6 8 .973b

81416.256,

71333.153,77064.04679660.71081057.669,

Level

6d 3D,6d 3D26d D3

7d 3Di7d 3D27d 3D3

8d 3Di8d 3D28d D3

9d 3D19d 3D29d D3

Wavenumber

71336.14-71396.18271431.281a

77084.58077107.87777129.509a

796 78.677b79690.25879702.573a

81070.95-81077.61481085.076a

10d D3 81913.577

a Only one line was available for the determination of this level.b The levels 10s 'Si. 1 s 'Si, 6d 3Di, 8d 3Di, and 9d 3Di are poorly deter-

mined because of near coincidence with lines of Hg-199.

TABLE MIla. Odd levels.

Wave WaveLevel number Level number

6p 3P°0 37645.092 8p 3P2 76823.518a

6p3P, 39412.301 8p'P0 , 78813.0786p 3P 2 44042.987 9P 'P0

1 79963.831

6p' Po1 54068.763

a Only one line was available for the determination of this level.

77107.993 deduced from the data of Schuler and Keyston5 or

77129.619 Schuler and Jones.' Column five shows the number ofobservations; here "C" indicates that the line was not

-----.--- observed but computed. Columns one, two, three andfive in italics contain data for Hg-200 similar to those

79690.364 for Hg-199 in columns one, two, three and five. The

79702.69- "M" in column five indicates that the value was foundby interpolation between the values for Hg-198 andHg-202, always near the mean.

81077.715 The data of column four, Table I, were derived byusing our values for the wave numbers of the evenisotopes and the differences given by Schuler et al. 56

6

his level. Thus, for 5790A our mean wave number for 198, 200,

and 202 is 17264.391. The differences -680, -499,and +361 lead to the numbers in column four. Thesedata were not used in setting up the levels in Table II,excepting for the levels 8p'p', and 9plp'j.

39412.436 In Table II the third column contains the centers of

44043.116 gravity of the multiple levels. The centers were found byweighting the individual levels F+2, smaller numbers

54068.876 but the same relative weight as the conventional 2F+ 1.Thus:

76823.625

78813.086

79963.917

7s 3S,-3/2 Wt 2 Difference + 1.0681.068/3 =0.356;

c.g. is 62150.519.

In Table IV the first column contains the level desig-nation. The second and ninth columns, respectively,

I H. Schuler and J. E. Keyston, Z. Phys. 72, 423 (1931).6H. Schuler and E. G. Jones, Z. Phys. 79, 631 (1932).

Level

6S2 So -1/2

7s 'So1-/28s 1S0-1/29s So-1/21Os So-1/2

7s 3S-1/27s 'S,-3/28s 3S,-1/28s 3S,-3/295 3S,-1/29s 'S,-3/21Os 3S-1/21Os 3S,-3/2

6d D2-3/26d 'Dz-5/27d 'Dz-3/27d D2-5/28d 1D2-3/28d 1D2-5/29d 1Dr3/29d 1D2-5/2

6d 3D,-1/26d 3D,-3/26d 3D2-3/26d 3D2-5/26d 3D3-5/26d 3D3-7/27d 3D,-1/27d 3D,-3/27d 3D2-3/27d 3D2-5/27d 3D3-5/27d 3D3 -7/28d 3D,-1/28d D,-3/28d 3D2-3/28d 3D2-5/28d 3D3-5/28d 3D3-7/29d 3D1-1/29d 3D,-3/29d D2-3/29d 3D2-5/2

.

719October 1952

K. BURNS AND K. B. ADAMS

TABLE IV. Comparison of the levels of six isotopes of mercury.

1 2 3 4 5 6 7 8 9 10 11 12198 199 200 201 202 198- 204 204

Level Observed obs int obs int obs int obs 202 obs int

6p 3Po 37645.241 5.213 5.221 5.092 5.092 5.0238 5.016 4.907 0.3346p 3P1 39412.455 2.436 2.435 2.301 2.307 2.242 2.241 2.123 0.332 1.966 1.9576p 3P0 2 44043.130 3.116 3.110 2.987 2.982 2.919 2.917 2.800 0.330 2.633 2.6356p 'P5O 54068.894 8.876 8.876 8.763 8.761 8.702 8.701 8.595 0.299

8p 3PO2 76823.643 3.625 3.626 3.516 3.515 . .--- 3.356 0.2878p 'Pol 78813.086 3.086 3.083 3.078 3.067 3.051 3.059 3.044 0.042 3.029 3.0239p P 1 79963.928 3.917 3.915 3.831 3.833 3.785 3.790 3.714 0.214 3.601 3.605lop 'P0 2 81022.866 . . . . . .--- 2.541 0.325

6s2 SO 00000.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.0007s 'So 63928.332 8.316 8.316 8.204 8.209 8.145 8.155 8.057 0.275 7.921 7.9208s 'So 74404.672 4.652 4.654 4.545 4.540 4.486 4.481 4.376 0.2969s 'So 78404.432 4.414 4.414 4.301 4.300 4.246 4.241 4.136 0.296lOs 'So 80365.725 . . . . _ _ _ 5.413 0.312

7s 3S, 62350.537 0.519 0.521 0.419 0.415 0.361 0.361 0.264 0.273 0.126 0.1278s S, 73961.371 1.357 1.353 1.239 1.240 1.187 1.181 1.077 0.2949S S, 78216.329 6.306 6.311 6.196 6.197 . . 6.033 0.296lOs 3S 80268.103 8.08- 8.086 7.973 7.974 . . 7.814 0.289Its S, 81416.357 -.--- 6.339 6.250 6.225 -. … … 6.062 0.295

6d 1D2 71333.288 3.221 3.270 3.153 3.151 3.086 3.090 2.981 0.3077d D, 77064.175 4.148 4.157 4.046 4.039 - .-- 3.869 0.3068d D, 79660.846 0.82- 0.828 0.710 0.711 . .--- 0.543 0.3039d D2 81057.813 -.--- 7.800 7.669 7.673 . .--- 7.500 0.313

6d 3D, 71336.256 6.315 6.238 6.126 6.118 . .--- 5.947 0.3086d 3D2 71396.320 6.296 6.302 6.182 6.182 6.112 6.121 6.011 0.3096d 3D3 71431.411 1.393 1.393 1.281 1.275 . .--- 1.050 0.3067d 3Di 77084.710 4.703 4.692 4.580 4.577 . .--- 4.411 0.2997d 3D2 77108.009 7.993 7.991 7.877 7.875 . .-- 7.709 0.3007d 3D3 77129.637 9.619 9.619 9.506 9.501 . .-- 9.332 0.3058d D, 79678.810 -.--- 8.792 8.677 8.677 . .--- 8.511 0.2998d D2 79690.391 0.364 0.373 0.258 0.258 . .--- 0.092 0.2998d 3D8 79702.687 2.69- 2.669 2.572 2.256 . .--- 2.393 0.2949d 3Di 81071.118 -.--- 1.101 0.950 0.990 . .--- 0.831 0.2879d 3D2 81077.750 7.715 7.732 7.614 7.616 . .--- 7.450 0.3009d 3D3 81085.206 -.--- 5.188 5.076 5.072 . .--- 4.905 0.30110d 3D3 81913.639 -.--- 3.577 -- 3.395 0.244b

a 6p 3P'o Determinations are discordant.b lOd 3D3 The value of Hg-198 appears to be wrong.

contain the observed wave numbers of this level forHg-198 and Hg-202, not as published but as derived bythe use of Barrell's refraction formula.4 Column tenshows the differences between the wave numbers ofHg-198 and Hg-202 when the level 6s2 'So is set at zero.The third column repeats the center of gravity wavenumbers of Hg-199 from Table II. Column four con-tains the interpolation between the wave numbers of198 and 202 which fits the best-determined levels of199. These numbers are: column two minus 0.060times column ten. The levels 6d D2 and 6d 3D1 do notfit the scheme. The identification of the latter may be inerror but the components of the former are well es-tablished. In all other cases a difference greater than0.008 cm-' between columns three and four is asso-ciated with a poorly determined level. For the well-determined centers the median difference betweencolumns three and four is :10.002 cm-'. Since the in-dividual hfs level differences range from +1.068 to-0.180 the validity of the weighting system is well,confirmed for Hg-199. Column five repeats Table III,wave numbers of the levels of Hg-200. Column six

shows the numbers: Column two minus 0.446 timescolumn ten. The wave numbers for Hg-201 were de-duced from the observations of Schuler et a. 8' 6 in themanner described in connection with column four,Table I. Differences between the components of Hg-201and the even levels were used when the latter werewell separated; otherwise, differences between the com-ponents of Hg-201 and the AOW values for Hg-199were used. A level table was then set up, and the hfslevels were weighted F to form centers of gravity,which are shown in column seven. Column eight showsthe numbers: Column two less 0.645 times column ten.The median difference between columns seven andeight is 0.005 cm-'. This number is over twice aslarge as the corresponding value for Hg-199. Its greatersize may be due to the difficulty of observing Hg-201in natural mercury rather than to the use of a faultyweighting system.

Five lines of Hg-204 were observed by Schuler andKeyston5 and one by Sterner.7 These permit the deriva-

'John Sterner, Phys. Rev. 86, 139 (1952).

720 Vo. 42

ISOTOPES OF MERCURY-199 AND -200

TABLE V. Comparison of the wave numbers of certain lines in the spectra of six isotopes of mercury.

1 2 3 4 5 6 7 8X Level designation 198 199 cg 200 201 cg 202 204

6716 7s 'So-8p 'P0 , 14884.755 4.768 4.866 4.900 4.984 5.1086234 7s 'So-9p 'P0 , 16035.594 5.605 5.620 5.634 5.657 5.6805790 6p 'PI,-6d D2 17264.393 4.345 4.391 4.380 4.3865769 6p 'P0

1 -6d D2 17327.423 7.417 7.420 7.410 7.418

5460 6p 3PO2 - 7s 3't 18307.404 7.408 7.432 7.442 7.463 7.493a4916 6p'P0 -8s 'So 20335.781 5.777 5.784 5.784 5.7834358 6p'P0 -7s 3S, 22938.082 8.083 8.113 8.119 8.143 8.1604108 6p 'PI,-9s 'So 24335.538 5.538 5.538 5.544 5.5394077 6p 3P -7s So 24515.877 5.880 5.898 5.903 5.934 5. 9 5 5b

4046 6P 3P'o-7s 'Si 24705.300 5.303 5.322 5.335 5.3563341 6p 'P°2-8s S, 29918.241 8.241 8.257 8.268 8.2842893 6p P0 ,-8s S, 34548.914 8.920 8.939 8.941 8.9502752 6p PIo-8s S, 36316.133 6.150 6.146 6.167 6.1682536 6s2 So-6p 3P0P 39412.455 2.435 2.301 2.242 2.123 1.966

a 5460 Number by Sterner, Phys. Rev. 86, 139 (1952).b 4077 Number computed.

tion of seven levels, including the lowest; column eleven.The formula, column two minus 1.500 times columnten, fits these levels with a median discrepancy of40.004 cm-'; column twelve.

The empirical formulas used above serve to check therelative values of levels of the individual isotopes;they may not be reliable in comparing one isotopewith another. The levels of Hg-1988 "1 and Hg-202' areexact. But considerable error may have been intro-duced into our measurements of Hg-199 by the pres-ence of twenty-six percent of other isotopes. If thelevels of Hg-200 actually fall half-way between those ofHg-198 and Hg-202, our system is in error by 0.017 cm-'.An error of this size does not seem to be probable, yetwe prefer to delay theoretical discussion of isotopeshifts until the richest available isotopes have beenobserved.

The data in Table V columns three, four, five, andseven are AOW observed excepting that, in the firsttwo lines, columns four and five are from Schuler andKeyston.5 To obtain the centers of gravity of the linesof the odd isotopes the components were weighted bythe system of Hill.9 For the lines 5460 and 3341 the dataof column six are the differences of the levels of columncolumn seven, Table IV. The data of columns six andeight are from Schuler et al.' 6 excepting as noted. Itis evident that for the S-P combinations 5460A to3341A the center of gravity of Hg-199 fits Hg-198within the error of observation, with an indication of ashift toward Hg-200. For five lines which show themeasurable mean difference 0.031 cm-' between tkewave numbers of Hg-200 and Hg-202 the mean centerof gravity for Hg-201 is displaced from Hg-200 towardHg-202 by 0.007 cm-', an amount somewhat greaterthan the probable error of one difference. The wave

8 William F. Meggers and Karl G. Kessler, J. Opt. Soc. Am. 40,737-741 (1950).

9 E. L. Hill, Proc. Nat. Acad. Sci. 16, 68 (1930).

numbers of 2893A and 2752A are probably somewhat inerror.

Schuler et al.5' 6 published complete observations ofonly two lines which arise from combinations with aD-level. Our observations of the other D-levels are allimperfect because of the coincidence of some of thecomponents of the odd with the line of the even iso-topes. For the two yellow lines our numbers for Hg-199are exact and in good agreement with Schuler et al.The simple system of weighting which, for the S-Pcombinations shows the center of gravity of the oddlines to fit the progression of the even lines, does not dothe same for the P-D combinations. For seven well-determined S-P combinations one can say that theisotope shift is (nearly) the same for both levels, withHill's weights. For the P-D combinations either theshift or the weight is different. Where the isotope shiftis large, the odd line falls closer to the next lower eventhan to the higher, as noted by Schuler and Keyston.5

We were assisted in observing and computing byMr. James C. Hunter; Mrs. Helen Louise Emler andMrs. Esther M. Donahue each did part of the measuringand computing; Mrs. Jean Longwell helped with thecomputing.

We are indebted to the National Bureau of Standardsfor the loan of interferometer plates and separatorsand to E. U. Condon, W. F. Meggers, and CharlotteMoore Sitterly for encouragement and assistance. Wethank R. F. Mehl and the Carnegie Institute of Tech-nology for the loan of the quartz spectrograph whichwas used for the work.

We are indebted to Director Condon and Dr. Meggersof the National Bureau of Standards for a sample of8oHg 55 which was derived from radioactive gold incooperation with the United States Atomic EnergyCommission. The sample of 8oHg 99 was produced byCarbide and Carbon Chemical Division, Oak RidgeNational Laboratory, Y12 Area, and obtained onallocation from the Isotopes Division of the AEC,

721October 1952