Abstract

The ionization potential of the neutral plutonium atom, Pu i, has been determined by two- and three-step resonance photoionization observation of the threshold of ionization and of Rydberg series. The Rydberg series were observed by field ionization as series that converge to the first ionization limit and as autoionizing series that converge to the second and to several higher convergence limits. The threshold and Rydberg series were obtained through a number of two- and three-step pathways. The photoionization threshold value for the 239Pu i ionization potential is 48582(30) cm−1, and the more accurate value from the Rydberg series is 48604(1) cm−1 or 6.0262(1) eV.

© 1993 Optical Society of America

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  1. R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  8. E. F. Worden, B. Comaskey, J. Densberger, J. Christensen, J. M. McAfee, J. A. Paisner, J. G. Conway, “The ionization potential of neutral iron, Fe i, by multistep laser spectroscopy,” J. Opt. Soc. Am. B 1, 314–316 (1984).
    [CrossRef]
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    [CrossRef]
  10. K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
    [CrossRef]
  11. R. H. Page, C. S. Gudeman, “Completing the iron period: double-resonance, fluorescence-dip Rydberg spectroscopy and ionization potentials of titanium, vanadium, iron, cobalt, and nickel,” J. Opt. Soc. Am. B 7, 1761–1771 (1990), and references therein.
    [CrossRef]
  12. D. H. Smith, G. H. Hertel, “First ionization potentials of Th, Np, and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
    [CrossRef]
  13. J. Bauche, J. Blaise, M. Fred, “Second systeme du spectre d’arc du plutonium. Nouveaux pairs des spectres I et II et potential d’ionisation de Pu i,” C. R. Acad. Sci. 257, 2260–2263 (1963).
  14. J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974); “Ionization energies of the neutral actinides,” J. Chem. Phys. 59, 788–791 (1973).
    [CrossRef]
  15. K. Rajnak, B. W. Shore, “Regularities in s-electron binding energies in lNsM configurations,” J. Opt. Soc. Am. 68, 360–367 (1978).
    [CrossRef]
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  17. J. Blaise, M. Fred, R. G. Gutmacher, “Term analysis of the spectrum of neutral plutonium, Pu i,” J. Opt. Soc. Am. B 3, 403–418 (1986); “The atomic spectrum of plutonium,” Argonne Nat. Lab. Rep. ANL-83-95 (National Technical Information Service, U.S. Department of Commerce, Springfield, Va., 1984).
    [CrossRef]

1990 (1)

1989 (1)

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

1988 (1)

1986 (1)

1984 (1)

1982 (1)

1979 (1)

1978 (3)

1976 (3)

1974 (1)

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974); “Ionization energies of the neutral actinides,” J. Chem. Phys. 59, 788–791 (1973).
[CrossRef]

1969 (1)

D. H. Smith, G. H. Hertel, “First ionization potentials of Th, Np, and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
[CrossRef]

1963 (1)

J. Bauche, J. Blaise, M. Fred, “Second systeme du spectre d’arc du plutonium. Nouveaux pairs des spectres I et II et potential d’ionisation de Pu i,” C. R. Acad. Sci. 257, 2260–2263 (1963).

Avril, R.

Bajaj, P. N.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

Bauche, J.

J. Bauche, J. Blaise, M. Fred, “Second systeme du spectre d’arc du plutonium. Nouveaux pairs des spectres I et II et potential d’ionisation de Pu i,” C. R. Acad. Sci. 257, 2260–2263 (1963).

Bekov, G. I.

G. I. Bekov, V. S. Letokov, O. I. Mamveev, V. I. Mishin, “Discovery of long lived autoionizing state in the spectrum of the gadolinium atom,” JETP Lett. 28, 283–285 (1978).

Blaise, J.

Blancard, P.

Callender, C. L.

Carlson, L. R.

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, R. W. Solarz, “Radiative lifetimes, absorption cross sections, and the observation of high lying odd levels of 238U using multistep laser photoionization,” J. Opt. Soc. Am. 66, 846–853 (1976).
[CrossRef]

R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
[CrossRef]

Chakraborti, P. K.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

Chatelet, J.

Christensen, J.

Comaskey, B.

Conway, J. G.

Coste, A.

Dasgupta, K.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

Densberger, J.

Fred, M.

J. Blaise, M. Fred, R. G. Gutmacher, “Term analysis of the spectrum of neutral plutonium, Pu i,” J. Opt. Soc. Am. B 3, 403–418 (1986); “The atomic spectrum of plutonium,” Argonne Nat. Lab. Rep. ANL-83-95 (National Technical Information Service, U.S. Department of Commerce, Springfield, Va., 1984).
[CrossRef]

J. Bauche, J. Blaise, M. Fred, “Second systeme du spectre d’arc du plutonium. Nouveaux pairs des spectres I et II et potential d’ionisation de Pu i,” C. R. Acad. Sci. 257, 2260–2263 (1963).

M. Fred, Argonne National Laboratory, Argonne, Ill. 60439 (personal communications, 1976–1983). J. Blaise, M. Fred, R. G. Gutmacher, “The atomic spectrum of plutonium,” Argonne Nat. Lab. Rep. ANL-83-95 (National Technical Information Service, U.S. Department of Commerce, Springfield, Va., 1984).

Gudeman, C. S.

Gutmacher, R. G.

Hackett, P. A.

Hertel, G. H.

D. H. Smith, G. H. Hertel, “First ionization potentials of Th, Np, and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
[CrossRef]

Johnson, S. A.

R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
[CrossRef]

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, R. W. Solarz, “Radiative lifetimes, absorption cross sections, and the observation of high lying odd levels of 238U using multistep laser photoionization,” J. Opt. Soc. Am. 66, 846–853 (1976).
[CrossRef]

Lambert, D.

Legre, J.

Letokov, V. S.

G. I. Bekov, V. S. Letokov, O. I. Mamveev, V. I. Mishin, “Discovery of long lived autoionizing state in the spectrum of the gadolinium atom,” JETP Lett. 28, 283–285 (1978).

Liberman, S.

Mamveev, O. I.

G. I. Bekov, V. S. Letokov, O. I. Mamveev, V. I. Mishin, “Discovery of long lived autoionizing state in the spectrum of the gadolinium atom,” JETP Lett. 28, 283–285 (1978).

Manohar, K. G.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

May, C. A.

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, R. W. Solarz, “Radiative lifetimes, absorption cross sections, and the observation of high lying odd levels of 238U using multistep laser photoionization,” J. Opt. Soc. Am. 66, 846–853 (1976).
[CrossRef]

R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
[CrossRef]

McAfee, J. M.

Mishin, V. I.

G. I. Bekov, V. S. Letokov, O. I. Mamveev, V. I. Mishin, “Discovery of long lived autoionizing state in the spectrum of the gadolinium atom,” JETP Lett. 28, 283–285 (1978).

Page, R. H.

Paisner, J. A.

Pinard, J.

Radziemski, L. J.

R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
[CrossRef]

J. Blaise, L. J. Radziemski, “Energy levels of neutral atomic uranium (U i),” J. Opt. Soc. Am. 66, 644–659 (1976).
[CrossRef]

Rajnak, K.

Rao, P. R. K.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

Rayner, D. M.

Shore, B. W.

Smith, D. H.

D. H. Smith, G. H. Hertel, “First ionization potentials of Th, Np, and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
[CrossRef]

Solarz, R. W.

Sugar, J.

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974); “Ionization energies of the neutral actinides,” J. Chem. Phys. 59, 788–791 (1973).
[CrossRef]

Talukdar, R.

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

Worden, E. F.

Appl. Phys. B (1)

K. G. Manohar, P. N. Bajaj, R. Talukdar, K. Dasgupta, P. K. Chakraborti, P. R. K. Rao, “Observation of autoionization resonances in uranium by step-wise laser photoionization,” Appl. Phys. B 48, 525–530 (1989).
[CrossRef]

C. R. Acad. Sci. (1)

J. Bauche, J. Blaise, M. Fred, “Second systeme du spectre d’arc du plutonium. Nouveaux pairs des spectres I et II et potential d’ionisation de Pu i,” C. R. Acad. Sci. 257, 2260–2263 (1963).

J. Chem. Phys. (2)

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974); “Ionization energies of the neutral actinides,” J. Chem. Phys. 59, 788–791 (1973).
[CrossRef]

D. H. Smith, G. H. Hertel, “First ionization potentials of Th, Np, and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
[CrossRef]

J. Opt. Soc. Am. (6)

J. Opt. Soc. Am. B (4)

JETP Lett. (1)

G. I. Bekov, V. S. Letokov, O. I. Mamveev, V. I. Mishin, “Discovery of long lived autoionizing state in the spectrum of the gadolinium atom,” JETP Lett. 28, 283–285 (1978).

Phys. Rev. A (1)

R. W. Solarz, C. A. May, L. R. Carlson, S. A. Johnson, J. A. Paisner, L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976).
[CrossRef]

Other (1)

M. Fred, Argonne National Laboratory, Argonne, Ill. 60439 (personal communications, 1976–1983). J. Blaise, M. Fred, R. G. Gutmacher, “The atomic spectrum of plutonium,” Argonne Nat. Lab. Rep. ANL-83-95 (National Technical Information Service, U.S. Department of Commerce, Springfield, Va., 1984).

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Figures (9)

Fig. 1
Fig. 1

Excitation schemes used in experiments to find photoionization thresholds and Rydberg series in atomic Pu. Series converging to the ground state of the ion were observed through field ionization with pulsed high-voltage fields. The delay between lasers in the sequence was at least 30 ns.

Fig. 2
Fig. 2

Photoionization threshold and autoionization of Pu observed by two-step laser excitation of an atomic beam. The excitation scheme is shown. The two strong autoionization peaks and the onset of a continuum background indicate the photoionization threshold.

Fig. 3
Fig. 3

Three-step photoionization threshold of Pu i through the excitation scheme shown. The dashed line is the zero-ion-signal level and indicates the presence of an ionization continuum. Two strong wide autoionization features plus at least seven weaker features appear in this range No λ1 + 2 λ2 features are present on this portion of the scan, but such features were observed at higher frequencies and were used for calibration.

Fig. 4
Fig. 4

Photoionization threshold of Pu i from the J = 0, 31 831-cm−1 level for the three-step excitation scheme shown. Three autoionization features are present in this scan as compared with more than 10 in Fig. 3 for the same energy range from a J = 1 level. This is to be expected, because only J = 1 levels can be obtained from the J = 0 level, while J = 0, 1, 2 levels can be reached from the J = 1 level.

Fig. 5
Fig. 5

Autoionizing Rydberg series from the J = 0 even level at 32 324.154 cm−1 converging to the first excited level of Pu ii at 2015 cm−1. The excitation scheme used is shown. The effective quantum number and the total excitation energy are given as horizontal axes. Perturbation of the series occurs near n* = 34. The 13 members identified with vertical ticks were used to determine the convergence limit; see Fig. 6. A λ1 + 2λ2 line masks some high series members, but it serves as a calibration point.

Fig. 6
Fig. 6

Plot of nn* versus n for various assumed limits for the series from the 32 324-cm−1 level. The value of n is not the principle number but is a whole number near n* in value. The value of n* is derived from Eq. (1). As is apparent, the most constant nn* value is given for the assumed limit value of 50 619 cm−1 When this value is corrected by the 2015 cm−1 energy of the Pu ii excited state, the IP value of 48 604 cm−1 is obtained.

Fig. 7
Fig. 7

Rydberg series converging to the ground state of the ion produced by field ionization of levels populatod from the 31 831-cm−1 level. The excitation scheme is shown. A field of 1000 V was applied 1 μs after the scan laser, λ3 pulse. The scan is essentially free of the shorter-lived valence levels with limits at least 2015 cm−1 higher in energy.

Fig. 8
Fig. 8

Scan of an autoionizing level at ~48 871 cm−1 exhibiting isotope shift and hfs. The relative frequency scale was established by use of a 300-MHz confocal étalon that monitored the scanning cw ring laser to produce fringes (not shown) recorded on the other pen of the two-pen recorder. The transition is from a J = 0 level as shown in the excitation scheme, so the hfs is associated with the J = 1 autoionization level. The linewidth of the autoionization is 1.8(1) GHz, with the isotope shift −5.6(1) GHz and the hfs splitting +2.6(1) GHz.

Fig. 9
Fig. 9

Portion of an autoionizing Rydberg series showing high members at higher resolution than the series shown in Fig. 5. The doublet structure of the series members identified by n* results from hfs splitting of the autoionizing levels. The 239Pu isotope with nuclear spin 1/2 was used, and, as shown in the excitation scheme, the series parent level has J = 0, so all Rydberg levels have J = 1 and two hfs components (F = 1/2, 3/2). The series was obtained with a N2-laser-pumped dye laser system consisting of a pressure-scanned high-angle grating and confocal étalon. An accurate relative frequency scale of approximately ±0.02 cm−1 was obtained with fringes from a 14.16-GHz étalon, but the absolute frequency was at least a factor of 10 less accurate.

Tables (5)

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Table 1 Plutonium First IP Values (239Pu) Obtained by Various Techniques

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Table 2 Lowest Levels of 239Pu i and 239Pu iia

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Table 3 Photoionization Thresholds Observed by Two- and Three-Step Laser Excitation from the 239Pu Ground, J = 0 Level in an Atomic Beama

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Table 4 Convergence Limits and IP Values Derived from Various Rydberg Series Observed with 239Pu as an Atom Sourcea

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Table 5 Frequenciesa of a J = 1 Autoionization Rydberg Series, from the 33 304.519 cm−1, J = 0 Level of 239Pu, that Shows hfs Splitting of +0.15(2) cm−1

Equations (1)

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n * = [ R / ( ionization limit level value ) ] 1 / 2 ,

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