Section: 10 | Persistent Lines Spectra of the Neutral Atomic Elements |

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One or more tables in this document differ to those in the book. This is due to space restrictions in the book.

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The table 'TABLE 1. Persistent Lines of Neutral Atomic Elements — Hydrogen I (Z = 1) to Helium I (Z = 2)' has one or more different columns to those in the book version.
The table 'TABLE 2. Persistent Lines of Neutral Atomic Elements — Lithium I (Z = 3) to Neon I (Z = 10)' has one or more different columns to those in the book version.
The table 'TABLE 8. Persistent Lines of Neutral Atomic Elements — Francium I (Z = 87) to Einsteinium I (Z = 99)' has one or more different columns to those in the book version.
The table 'TABLE 3. Persistent Lines of Neutral Atomic Elements — Sodium I (Z = 11) to Argon (Z = 18)' has one or more different columns to those in the book version.
The table 'TABLE 4. Persistent Lines of Neutral Atomic Elements — Potassium I (Z = 19) to Krypton (Z = 36)' has one or more different columns to those in the book version.
The table 'TABLE 5. Persistent Lines of Neutral Atomic Elements — Rubidium (Z = 37) to Xenon (Z = 54)' has one or more different columns to those in the book version.
The table 'TABLE 7. Persistent Lines of Neutral Atomic Elements — Lanthanum I (Z = 57) to Lutetium I (Z = 71)' has one or more different columns to those in the book version.
The table 'TABLE 6. Persistent Lines of Neutral Atomic Elements — Cesium I (Z = 55), Barium I (Z = 56), and Hafnium I (Z = 72) to Radon I (Z = 86)' has one or more different columns to those in the book version.

How to Cite this Reference

PERSISTENT LINES OF THE NEUTRAL ATOMIC ELEMENTS

Yuri Ralchenko and Alexander Kramida

The persistent lines in the spectra of atomic elements are the lines that are observed even at very low amounts of an element within a multielement sample. Such lines are useful for identifying the occurrence of an element even at quite small concentrations. Persistent lines are also called the “ultimate” lines for an element. The strongest persistent lines almost always contain the resonance lines, that is, the lines for transitions from a higher state to the ground state.

The data in these tables are from the NIST physical reference databases (Refs. 1-2) and include at least one of the resonance lines for each spectrum. The most sensitive or ultimate lines for many spectra lie in the vacuum-ultraviolet region (wavelength < 2000 Å). In such cases, NIST has included, when possible, some lines above 2000 Å in the persistent lines list. The data covers broader wavelength ranges than most tables of this sort. For all transitions with wavenumbers greater than 50,000 cm⁻¹, the wavelengths listed are vacuum wavelengths; for those less than 50,000 cm⁻¹, air wavelengths are given.

The list of persistent lines includes the energy levels involved in the transition, complete with configuration, term designations, and J values.

Persistent Line Spectra

These spectra cover the neutral atomic elements in order of atomic number Z from Hydrogen (Z = 1) to Einsteinium (Z = 99) and are grouped into eight tables, based on the common arrangement in the Periodic Table. Each spectrum is arranged in two rows. The upper row contains information about the line and transition probability as well as data on the lower state. The second row contains data on the upper state. Column definitions for the two-row sets in Tables 1 to 8 are as follows.

Column heading	Definition
Intensity	Observed relative intensity on an arbitrary scale that is different for each element; the meaning of character symbols appearing after the numerical value of intensity is explained in the table below; see also NIST ASD Help pages <https://physics.nist.gov/PhysRefData/ASD/Html/lineshelp.html#OUTRELINT>
Wavelength	Observed wavelength in ångströms (Å); wavelengths between 2000 Å and 20000 Å are given in standard air (15 °C, 0.033% CO₂); outside of this range, the wavelengths are in air; conversion between vacuum and air was made by NIST using the 5-parameter formula in Ref. 3
Uncert. wavelength	Uncertainty of observed wavelength in ångströms (Å); blank if not available
A_ki	Radiative transition probability, in units of 10⁸s^-1
f_ik	Absorption oscillator strength (dimensionless) [Online Edition only]
S	Line strength (atomic units) [Online Edition only]
Accur.	Accuracy code for A_ki; see also <https://physics.nist.gov/PhysRefData/ASD/Html/lineshelp.html#OUTACC>
Energy levels	In the first row, energy of the lower level, in cm^-1 (wavenumber); in the second row, energy of the upper level, in cm^-1 (wavenumber)
Configs.	Configuration and number of outermost electrons. In the first row, configuration of the lower level; in the second row, configuration of the upper level; if a single number, e.g., "5" appears as a configuration, the sub-shell is unknown
Terms	The spectroscopic Term Symbol of the element for the specified configuration; in the first row, the term symbol of the lower level; in the second row, the term symbol of the upper level (see discussion below)
J	The total angular momentum quantum number J for the specified configuration; in the first row, the J value for the lower level; in the second row, the J value for the upper level
g	The statistical weight for the specified configuration; the first row is the statistical weight for the lower level; in the second row, the statistical weight for the upper level
DB Source	Reference to the primary source of the listed data (ASD = <https://physics.nist.gov/ASD>; HDBK = <https://physics.nist.gov/handbook>)

Intensities

The meanings of the character symbols appearing after the numerical value of intensity are as follows.

Symbol	Meaning
*	Intensity is shared by several lines (typically for multiply classified lines)
:	Observed value given is actually the rounded Ritz value, e.g., Ar IV, λ = 443.40 Å
-	Somewhat lower intensity than the value given
a	Observed in absorption
b	Band head
bl	Blended with another line that may affect the wavelength and intensity
B	Line or feature having large width due to autoionization broadening
c	Complex line
d	Diffuse line
D	Double line
E	Broad due to overexposure in the quoted reference
f	Forbidden line
g	Transition involving a level of the ground term
G	Line position roughly estimated
H	Very hazy line
h	Hazy line (same as "diffuse")
hfs	Line has hyperfine structure
i	Identification uncertain
j	Wavelength smoothed along isoelectronic sequence
l	Shaded to longer wavelengths; NB: This may look like a "one" at the end of the number
m	Masked by another line (no wavelength measurement)
p	Perturbed by a close line. Both wavelength and intensity may be affected
q	Asymmetric line
r	Easily reversed line
s	Shaded to shorter wavelengths
t	Tentatively classified line
u	Unresolved from a close line
w	Wide line
x	Extrapolated wavelength

Transition Probabilities

The values are listed as A_ki in units of 10⁸s^-1. These A_ki values can easily be converted to oscillator strengths, f_ik, g_if_ik, or log(g_if_ik), or line strength, S, by using the following formula:

g_if_ik = 1.499 × 10^-8A_ki λ²g_k = 303.8 λ^-1S

where i refers to the lower energy level, k refers to the upper level, λ is the wavelength in angströms, and g = 2J + 1 for a given level.

The NIST transition-probability values include values with uncertainties ranging from 1% to larger than 50%, with an approximate uncertainty range being indicated for each line by an assigned letter. We have not included or assigned such letters here, but this information is given in the NIST publications and in the NIST online database for all transition-probability values taken from these sources. For data taken from the original literature or from non-NIST compilations, the user can consult the cited references for accuracy estimates. The reference list for the transition probabilities is given in the Online Edition of the CRC Handbook. See also the table "Atomic Transition Probabilities" in this section.

Accuracy

An estimated accuracy is listed for each transition strength, indicated by a code letter as given in the table below:

Accuracy code	Accuracy value
AAA	≤0.3%
AA	≤1%
A+	≤2%
A	≤3%
B+	≤7%
B	≤10%
C+	≤18%
C	≤25%
D+	≤40%
D	≤50%
E	>50%

The uncertainties are obtained from critical assessments, and in general, reflect estimates of predominantly systematic effects discussed in the NIST critical compilations, as cited in the references therein. If the accuracy is followed by a prime (′), then a multiplet in the original compilation has been separated into its component lines and the transition probability was derived from the compiled value assuming spin-orbit coupling. This may decrease the listed accuracy, especially for weaker transitions.

Energy-Level Classifications

Data pertaining to the two energy levels classifying each line are given with data for the lower level above that for the upper level. Included are the level values, configurations, term names, and J values for the levels classifying the line. The energy-level classifications for a few persistent lines are not known, as indicated by the absence of level values.

Terms

Terms of the lower and upper levels are displayed. A superscript "°" or an asterisk indicates odd parity. The J values represent the total electronic angular momentum of the lower and upper levels. g_i and g_k represent the statistical weights of the lower level (g_i= 2J_i+ 1) and upper level (g_k= 2J_k + 1), respectively.

For atoms with more than two d-electrons, the normal (2S + 1)L is not unique. Generally, a seniority number is used, but for some cases, the terms with the same (2S + 1)L value are labeled by letters. The first even parity of a certain LS symmetry is labeled as "a ^2S+1L;" the second as "b ^2S+1L;" etc. The odd-parity terms are labeled in reverse alphabetical order starting with "z."

Integer numbers are often used instead of term symbols when the levels have not been theoretically interpreted or when the eigenvectors are so strongly mixed that assignment of proper term labels to each level is meaningless. For example, in the case of Ir I, there is no theoretical interpretation of highly excited odd-parity levels, so the labels are unknown. The integer labels for these levels of Ir I are the left four numerals of the level energy.

Such assignment (intended to provide a unique correspondence between the level and line lists) is not always done; in many cases the level labels are left blank; then the "º" symbol appearing in the Terms column represent the only information known about the nature of the level, i.e., parity is odd. It would be even if the label is completely blank.

References

Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (20l7). NIST Atomic Spectra Database (Version 5.5.1) [Online]. Available: <https://physics.nist.gov/asd> [Dec. 29, 2017]. National Institute of Standards and Technology, Gaithersburg, MD.
J. E. Sansonetti, W. C. Martin, and S. L. Young (2005), Handbook of Basic Atomic Spectroscopic Data (Version 1.1.2) [Online], Available: <http://physics.nist.gov/Handbook> [Dec. 29, 2017]. National Institute of Standards and Technology, Gaithersburg, MD.
E. R. Peck and K. Reeder, J. Opt. Soc. Am. 62, 958–962, 1972. [https://doi.org/10.1364/JOSA.62.000958]

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Mobile-friendly table

TABLE 1. Persistent Lines of Neutral Atomic Elements — Hydrogen I (Z = 1) to Helium I (Z = 2)

Name	Intensity	Wavelength/Å	Uncert. wavelength/Å	A_ki/(10⁸s^-1)	Accur.	Energy levels/cm^-1	Configs.	Terms	J	g	DB Source	A_ki Ref.	Line Ref.
Continued on next page...
Hydrogen I (Z = 1)
Hydrogen		949.742	0.004	0.34375	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						105291.65209	5p	²Pº	3/2	4
Hydrogen	33000	949.742	0.004	0.041250	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						105291.657	5			50
Hydrogen		949.742	0.004	0.34375	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						105291.62867	5p	²Pº	1/2	2
Hydrogen	83000	972.517	0.014	0.12785	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L8834
Hydrogen						102823.904	4			32
Hydrogen		972.541	0.019	0.68186	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L8445
Hydrogen						102823.8943175	4p	²Pº	3/2	4
Hydrogen		972.541	0.019	0.68186	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L8445
Hydrogen						102823.8485825	4p	²Pº	1/2	2
Hydrogen		1025.728	0.003	1.6725	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						97492.319611	3p	²Pº	3/2	4
Hydrogen	250000	1025.728	0.003	0.55751	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						97492.304	3			18
Hydrogen		1025.728	0.003	1.6725	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L3545
Hydrogen						97492.211200	3p	²Pº	1/2	2
Hydrogen		1215.6699	0.0020	6.2648	AAA	0.0000000000	1s	²S	1/2	2	ASD	T8637	L12020

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