K

Click on a "Nuclear data" button to display properties of isotopes with a half-life exceeding 10 minutes (3 minutes for Fr).
Click on a "Hyperfine constant A" button to display the values of magnetic-dipole hyperfine constants A (in MHz) complied from published papers.
If the atom/ion has metastable states a "Metastable state properties" button will show with a list of metastable states. Click on the button to display the data for dominant electric quadrupole (E2) and magnetic dipole (M1) transitions, lifetimes, and quadrupole moments.
Click on a "Ref" button to display the sources of the data.
Click on the "Print" button to print the tables you see on the screen.

Isotope info	Mass number	Symbol	Half-life info	Natural abundance (%) info	Nuclear spin	Rms radii (fm) info	Rms radii (fm)	Uncertainty (fm)	Magnetic moment (μ_N) info	Magnetic moment (μ_N)	Uncertainty (μ_N)	Quadrupole moment (b) info	Quadrupole moment (b)	Uncertainty (b)
³⁹K	39	K	Stable	93.26	3/2	3.4349(19)	3.4349	0.0019	0.391470(8)	0.39147	8e-06	0.0585(6)	0.0585	0.0006
⁴⁰K	40	K	1.3x10⁹ years	0.012	4	3.4381(28)	3.4381	0.0028	-1.29797(3)	-1.29797	3e-05	-0.073(1)	-0.073	0.001
⁴¹K	41	K	Stable	6.73	3/2	3.4518(55)	3.4518	0.0055	0.214872(5)	0.214872	5e-06	0.0711(7)	0.0711	0.0007
⁴²K	42	K	12.36 hours		2	3.4517(70)	3.4517	0.007	-1.1425(6)	-1.1425	0.0006
⁴³K	43	K	22.3 hours		3/2	3.4556(86)	3.4556	0.0086	0.1633(8)	0.1633	0.0008
⁴⁴K	44	K	22.1 minutes		2	3.4563(101)	3.4563	0.0101	-0.856(4)	-0.856	0.004
⁴⁵K	45	K	17.8 minutes		3/2	3.4605(118)	3.4605	0.0118	0.1734(8)	0.1734	0.0008

Isotope	State	Theory	Key1 info	Experiment	Key2 info	Reference1 info	DOI1 info	Reference2 info	DOI2 info
³⁹K	4s_1/2			230.8598601(7)	E29			A. Beckmann , K. D. Boklen, and D. Elke, Z. Phys. 270, 173 (1974)	https://doi.org/10.1007/BF01680407
	5s_1/2	54.817	E40	55.50(60)	E4	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	R. Gupta, W. Happer, L. K. Lam, and S. Svanberg, Phys. Rev. A 8, 2792 (1973)	https://doi.org/10.1103/PhysRevA.8.2792
	6s_1/2	21.609	E40	21.81(18)	E4	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	R. Gupta, W. Happer, L. K. Lam, and S. Svanberg, Phys. Rev. A 8, 2792 (1973)	https://doi.org/10.1103/PhysRevA.8.2792
	7s_1/2	10.69	E40	10.78(5)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	8s_1/2	6.057	E40	5.99(8)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	9s_1/2	3.759	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
	10s_1/2	2.491	E40	2.41(5)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	4p_1/2	27.662	E40	27.775(42)	E32	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	5p_1/2	8.949	E40	8.99(15)	E33	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	W. N. Fox and G. W. Series, Proc. Phys. Soc. Lond. 77, 1141 (1961)	10.1088/0370-1328/77/6/305
	6p_1/2	4.014	E40	4.05(7)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	7p_1/2	2.14	E40	2.18(5)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	4p_3/2	5.989	E40	6.093(25)	E32	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	5p_3/2	1.932	E40	1.969(13)	E3	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	E. Arimondo, M. Inguscio, and P. Violino, Rev. Mod. Phys. 49, 31 (1977)	https://doi.org/10.1103/RevModPhys.49.31
	6p_3/2	0.866	E40	0.866(8)	E36	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	S. Svanberg, Phys. Scr. 4, 275 (1971)	https://doi.org/10.1088/0031-8949/4/6/007
	7p_3/2	0.462	E40	0.49(4)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	3d_3/2	1.111	E40	0.96(4)	E41	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
	3d_5/2	-0.639	E40	0.62(4)	E41	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
	4d_3/2	0.678	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
	4d_5/2	-0.307	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
	5d_3/2	0.409	E40	0.44(10)	E30	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	G. Belin, L. Holmgren, I. Lindgren, and S. Svanberg, Phys. Scr. 12, 287 (1975)	https://doi.org/10.1088/0031-8949/12/5/007
	5d_5/2	-0.167	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
	6d_3/2	0.253	E40	0.25(1)	E42	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	M. Głódź and M. Kraińska-Miszczak, J. Phys. B 18, 1515 (1985)	https://doi.org/10.1088/0022-3700/18/8/010
	6d_5/2	-0.0975	E40	-0.12(4)	E42	U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504	M. Głódź and M. Kraińska-Miszczak, J. Phys. B 18, 1515 (1985)	https://doi.org/10.1088/0022-3700/18/8/010
	7d_3/2	0.1644	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
	7d_5/2	-0.0611	E40			U. I. Safronova and M. S. Safronova, Phys. Rev. A 78, 052504 (2008)	https://doi.org/10.1103/PhysRevA.78.052504
⁴⁰K	4s_1/2			-285.7308(24)	E3			E. Arimondo, M. Inguscio, and P. Violino, Rev. Mod. Phys. 49, 31 (1977)	https://doi.org/10.1103/RevModPhys.49.31
	4p_1/2			-34.523(25)	E32			S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	4p_3/2			-7.585(10)	E32			S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	3d_3/2			1.07(2)	E37			A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
	3d_5/2			0.71(4)	E37			A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
⁴¹K	4s_1/2			127.0069352(6)	E3			E. Arimondo, M. Inguscio, and P. Violino, Rev. Mod. Phys. 49, 31 (1977)	https://doi.org/10.1103/RevModPhys.49.31
	4p_1/2			15.245(42)	E32			S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	4p_3/2			3.363(25)	E32			S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, and G. Grosche, Phys. Rev. A 74, 032503 (2006)	https://doi.org/10.1103/PhysRevA.74.032503
	3d_3/2			0.55(3)	E37			A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
	3d_5/2			0.40(2)	E37			A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)
	5s_1/2			30.75(75)	E4			R. Gupta, W. Happer, L. K. Lam, and S. Svanberg, Phys. Rev. A 8, 2792 (1973)	https://doi.org/10.1103/PhysRevA.8.2792
	6s_1/2			12.03(40)	E4			R. Gupta, W. Happer, L. K. Lam, and S. Svanberg, Phys. Rev. A 8, 2792 (1973)	https://doi.org/10.1103/PhysRevA.8.2792
	6d_3/2			0.14(2)	E37			A. Sieradzan, R. Stoleru, W. Yei, and M. D. Havey, Phys. Rev. A 55, 3475 (1997)

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