Abstract

The first ionization potential of neptunium has been determined from the photoionization threshold and from Rydberg series observed by laser spectroscopy techniques. The Rydberg series convergence limits yield the most accurate value of 50 536(4) cm−1 [6.2657(5) eV]. The radiative lifetimes of five levels in the 26 200–29 050-cm−1 range have been measured. New energy levels, 27 odd and 37 even, in the 33 000–37 000-cm−1 range have been determined with approximately ± 0.5-cm−1 precision.

© 1979 Optical Society of America

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  1. L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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]
  2. R. W. Solarz, C. A. May, L. R. Carlson, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
    [Crossref]
  3. D. H. Smith and G. R. Hertel, “First ionization potentials of Th, Np and Pu by surface ionization,” J. Chem. Phys. 51, 3105–3107 (1969).
    [Crossref]
  4. E. G. Rauh and R. J. Ackermann, “The first ionization potentials of neptunium and neptunium monoxide,” J. Chem. Phys. 62, 1584 (1975).
    [Crossref]
  5. J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974).
    [Crossref]
  6. M. Fred and F. S. Tomkins, Argonne National Laboratory, Argonne, II.;J. E. Blaise, P. Camus, J. Verges, and Laboratoire Aimé Cotton, Orsay, France, “The atomic spectrum of neptunium,” Argonne National Laboratory, report ANL-76-68, May, 1976 available from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA. 22161, $8.00, microfiche $2.25.
  7. M. Fred, F. S. Tomkins, J. E. Blaise, P. Camus, and J. Verges, “Term analysis of neutral neptunium (Np i),” J. Opt. Soc. Am. 67, 7–23 (1977).
    [Crossref]
  8. R. J. Ackermann pointed out the need to use single crystal tantalum to contain Np metal at high temperature and also emphasized that NpO would be the major species during the initial stages of vaporization, (private communication, 1977).
  9. R. J. Ackermann and E. G. Rauh, “The thermodynamics of vaporization of neptunium and plutonium,” J. Chem. Thermodynamics 7, 211–218 (1975).
    [Crossref]
  10. We are indebted to J. Blaise, Laboratoire Aimé Cotton, Orsay, Franceand M. Fred, Argonne National Laboratory, Argonne, Il. for providing us with the unpublished low-lying energy levels of singly ionized Np.
  11. K. Rajnak and B. W. Shore, “Regularities in s-electron binding energies in lNsM configurations,” J. Opt. Soc. Am. 68, 360–367 (1978).
    [Crossref]

1978 (1)

1977 (1)

1976 (2)

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

1975 (2)

E. G. Rauh and R. J. Ackermann, “The first ionization potentials of neptunium and neptunium monoxide,” J. Chem. Phys. 62, 1584 (1975).
[Crossref]

R. J. Ackermann and E. G. Rauh, “The thermodynamics of vaporization of neptunium and plutonium,” J. Chem. Thermodynamics 7, 211–218 (1975).
[Crossref]

1974 (1)

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974).
[Crossref]

1969 (1)

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

Ackermann, R. J.

E. G. Rauh and R. J. Ackermann, “The first ionization potentials of neptunium and neptunium monoxide,” J. Chem. Phys. 62, 1584 (1975).
[Crossref]

R. J. Ackermann and E. G. Rauh, “The thermodynamics of vaporization of neptunium and plutonium,” J. Chem. Thermodynamics 7, 211–218 (1975).
[Crossref]

Blaise, J.

We are indebted to J. Blaise, Laboratoire Aimé Cotton, Orsay, Franceand M. Fred, Argonne National Laboratory, Argonne, Il. for providing us with the unpublished low-lying energy levels of singly ionized Np.

Blaise, J. E.

Camus, P.

Carlson, L. R.

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

Fred, M.

M. Fred, F. S. Tomkins, J. E. Blaise, P. Camus, and J. Verges, “Term analysis of neutral neptunium (Np i),” J. Opt. Soc. Am. 67, 7–23 (1977).
[Crossref]

M. Fred and F. S. Tomkins, Argonne National Laboratory, Argonne, II.;J. E. Blaise, P. Camus, J. Verges, and Laboratoire Aimé Cotton, Orsay, France, “The atomic spectrum of neptunium,” Argonne National Laboratory, report ANL-76-68, May, 1976 available from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA. 22161, $8.00, microfiche $2.25.

Hertel, G. R.

D. H. Smith and G. R. 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, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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]

May, C. A.

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

Paisner, J. A.

R. W. Solarz, C. A. May, L. R. Carlson, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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]

Radziemski, L. J.

R. W. Solarz, C. A. May, L. R. Carlson, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

Rajnak, K.

Rauh, E. G.

E. G. Rauh and R. J. Ackermann, “The first ionization potentials of neptunium and neptunium monoxide,” J. Chem. Phys. 62, 1584 (1975).
[Crossref]

R. J. Ackermann and E. G. Rauh, “The thermodynamics of vaporization of neptunium and plutonium,” J. Chem. Thermodynamics 7, 211–218 (1975).
[Crossref]

Shore, B. W.

Smith, D. H.

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

Solarz, R. W.

R. W. Solarz, C. A. May, L. R. Carlson, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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]

Sugar, J.

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974).
[Crossref]

Tomkins, F. S.

M. Fred, F. S. Tomkins, J. E. Blaise, P. Camus, and J. Verges, “Term analysis of neutral neptunium (Np i),” J. Opt. Soc. Am. 67, 7–23 (1977).
[Crossref]

M. Fred and F. S. Tomkins, Argonne National Laboratory, Argonne, II.;J. E. Blaise, P. Camus, J. Verges, and Laboratoire Aimé Cotton, Orsay, France, “The atomic spectrum of neptunium,” Argonne National Laboratory, report ANL-76-68, May, 1976 available from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA. 22161, $8.00, microfiche $2.25.

Verges, J.

Worden, E. F.

L. R. Carlson, J. A. Paisner, E. F. Worden, S. A. Johnson, C. A. May, and 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, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

J. Chem. Phys. (3)

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

E. G. Rauh and R. J. Ackermann, “The first ionization potentials of neptunium and neptunium monoxide,” J. Chem. Phys. 62, 1584 (1975).
[Crossref]

J. Sugar, “Revised ionization energies of the neutral actinides,” J. Chem. Phys. 60, 4103 (1974).
[Crossref]

J. Chem. Thermodynamics (1)

R. J. Ackermann and E. G. Rauh, “The thermodynamics of vaporization of neptunium and plutonium,” J. Chem. Thermodynamics 7, 211–218 (1975).
[Crossref]

J. Opt. Soc. Am. (3)

Phys. Rev. A (1)

R. W. Solarz, C. A. May, L. R. Carlson, E. F. Worden, S. A. Johnson, J. A. Paisner, and L. J. Radziemski, “Detection of Rydberg states in uranium using time-resolved stepwise laser photoionization,” Phys. Rev. A 14, 1129–1136 (1976);E. F. Worden, R. W. Solarz, J. A. Paisner, and J. G. Conway, “First ionization potentials of lanthanides by laser spectroscopy,” J. Opt. Soc. Am. 68, 52–61 (1978).
[Crossref]

Other (3)

R. J. Ackermann pointed out the need to use single crystal tantalum to contain Np metal at high temperature and also emphasized that NpO would be the major species during the initial stages of vaporization, (private communication, 1977).

M. Fred and F. S. Tomkins, Argonne National Laboratory, Argonne, II.;J. E. Blaise, P. Camus, J. Verges, and Laboratoire Aimé Cotton, Orsay, France, “The atomic spectrum of neptunium,” Argonne National Laboratory, report ANL-76-68, May, 1976 available from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA. 22161, $8.00, microfiche $2.25.

We are indebted to J. Blaise, Laboratoire Aimé Cotton, Orsay, Franceand M. Fred, Argonne National Laboratory, Argonne, Il. for providing us with the unpublished low-lying energy levels of singly ionized Np.

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Figures (5)

FIG. 1
FIG. 1

Neptunium photoionization threshold spectrum. The excitation scheme is shown at the left. The threshold at 4593 Å is marked by the onset of very strong autoionization peaks. It yields an ionization potential of 50518 cm−1 (6.2634 eV).

FIG. 2
FIG. 2

Plot of neptunium ion signal vs ionizing pulse delay time for the 28986-cm−1 odd level of neptunium. The transition and excitation wavelength are given in Table III. The wavelength of the ionizing laser was 4310 Å.

FIG. 3
FIG. 3

Rydberg series in neptunium obtained by field ionization (double arrow) of laser-excited levels. The excitation scheme is shown on the figure. The spectrum contains two series, one converging to the 4f46d7s 7L5 ground state and the other converging to the 5/4 level at 24.27 cm−1 in the ion. For the series converging to the 5/4 level, the Rydberg level positions with n* less than 40.7 (short markers) are calculated using a constant fractional defect of 0.3.

FIG. 4
FIG. 4

Variation in quantum defect (nn*) vs n with change in assumed ionization limit for the neptunium series in Fig. 3 converging to the ground state of the ion. The assumed limit giving the most constant quantum defect is 50536 cm−1 and is taken as the ionization limit.

FIG. 5
FIG. 5

Variation in quantum defect vs n with charge in assumed limit for the series in Fig. 3 converging to the 5/4 level in the ion. The assumed limit giving the most constant quantum defect is 50559 cm−1 and when corrected by 24.27 cm−1 yields the ionization limit of 50 535 cm−1 for neptunium.

Tables (6)

Tables Icon

TABLE I Photoionization thresholds obtained for neptunium by two-step laser excitation.

Tables Icon

TABLE II Rydberg series limits determined by stepwise laser excitation techniques for Np and ionization potentials derived.

Tables Icon

TABLE III First ionization potentials of neptunium determined by various techniques.

Tables Icon

TABLE IV Lifetimes of five excited states of neptunium and estimated branching ratios and transition probabilities.

Tables Icon

TABLE V High even levels of neptunium observed from the three odd levels given as headings for the first three colunms (excitation wavelength, energy and J value).

Tables Icon

TABLE VI High odd levels of Np obtained from the 19373.87 cm−1, J = 3.5 even level populated by λ1 at 6043.282A (2831–19373). The J of the upper levels observed could be 2.5, 3.5, or 4.5.

Equations (3)

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level value = limit [ R / ( n * ) 2 ]
n * = [ R / ( assumed limit level value ) ] 1 / 2 .
A = BR / τ