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Glans, Peter
Publikasjoner (10 av 53) Visa alla publikasjoner
Mahmood, S., Orban, I., Ali, S., Glans, P., Bleda, E. A., Altun, Z. & Schuch, R. (2013). RECOMBINATION RATE COEFFICIENTS OF BORON-LIKE Ne. Astrophysical Journal, 771(2), Art. no. 78
Åpne denne publikasjonen i ny fane eller vindu >>RECOMBINATION RATE COEFFICIENTS OF BORON-LIKE Ne
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2013 (engelsk)Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 771, nr 2, s. Art. no. 78-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Recombination of Ne5+ was measured in a merged-beam type experiment at the heavy-ion storage ring CRYRING. In the collision energy range 0-110 eV resonances due to 2s(2)2p -> 2s2p(2) (Delta n=0) and 2s(2)2p -> 2s(2)3l (Delta n=1), core excitations were observed. The experimentally derived rate coefficients agree well with the calculations obtained using AUTOSTRUCTURE. At low energies, recombination is dominated by resonances belonging to the spin-forbidden 2s2p(2)(P-4(J))nl series. The energy-dependent rate coefficients were convoluted with a Maxwell-Boltzmann electron energy distribution to obtain plasma recombination rate coefficients. The data from the literature deviate from the measured results at low temperature.

Emneord
atomic data, atomic processes, plasmas
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-20653 (URN)10.1088/0004-637X/771/2/78 (DOI)000321340700003 ()2-s2.0-84879346262 (Scopus ID)
Tilgjengelig fra: 2013-12-12 Laget: 2013-12-11 Sist oppdatert: 2017-12-06bibliografisk kontrollert
Ali, S., Orban, I., Mahmood, S., Altun, Z., Glans, P. & Schuch, R. (2012). ELECTRON-ION RECOMBINATION RATE COEFFICIENTS FOR C II FORMING C I. Astrophysical Journal, 753(2), Art. no. 132
Åpne denne publikasjonen i ny fane eller vindu >>ELECTRON-ION RECOMBINATION RATE COEFFICIENTS FOR C II FORMING C I
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2012 (engelsk)Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 753, nr 2, s. Art. no. 132-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We have determined absolute dielectronic recombination rate coefficients for C II, using the CRYRING heavy-ions storage ring. The resonances due to 2s-2p (Delta n= 0) core excitations are detected in the center-of-mass energy range of 0-15 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients are obtained from the DR spectrum by convoluting it with a Maxwell-Boltzmann energy distribution for temperatures in the range of 10(3)-10(6) K. The derived temperature-dependent plasma recombination rate coefficients are presented graphically and parameterized by using a fit formula for convenient use in plasma modeling codes. The experimental rate coefficients are also compared with the theoretical data available in literature. In the temperature range of 10(3)-2 x 10(4) K, our experimental results show that previous calculations severely underestimate the plasma rate coefficients and also our AUTOSTRUCTURE calculation does not reproduce the experimental plasma rate coefficients well. Above 2x10(4) K, the agreement between the experimental and theoretical rate coefficients is much better, and the deviations are smaller than the estimated uncertainties.

Emneord
atomic data, atomic processes, plasmas
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-17059 (URN)10.1088/0004-637X/753/2/132 (DOI)000305912700039 ()2-s2.0-84862868343 (Scopus ID)
Tilgjengelig fra: 2012-10-08 Laget: 2012-09-26 Sist oppdatert: 2017-12-07bibliografisk kontrollert
Orban, I., Loch, S. D., Glans, P., Böhm, S. & Schuch, R. (2011). Effects of spin-forbidden resonances on the recombination of Be-like Si and Be-like Ne. Paper presented at Conference: 15th International Conference on the Physics of Highly Charged Ions, HCI2010 Location: Fudan Univ, Shanghai, PEOPLES R CHINA Date: AUG 29-SEP 03, 2010. Physics Scripta, T144, Art. no. 014035
Åpne denne publikasjonen i ny fane eller vindu >>Effects of spin-forbidden resonances on the recombination of Be-like Si and Be-like Ne
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2011 (engelsk)Inngår i: Physics Scripta, ISSN 0031-8949, Vol. T144, s. Art. no. 014035-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Recombination through doubly excited states that can be formed only through spin-flip of the excited electrons can give very strong contributions to the recombination rate of Be-like ions. We demonstrate this, in this paper, with the electron-ion recombination spectra of Be-like Ne(6+) and Be-like Si(10+), recently measured at the CRYRING storage ring. These resonances have significant effects on the plasma rate coefficients. We show that neglect or imprecise calculation of these resonances is responsible for large spreads observed between various theoretical results from the literature.

sted, utgiver, år, opplag, sider
IOP Publishing Ltd, 2011
Emneord
FINITE-DENSITY PLASMAS; DIELECTRONIC RECOMBINATION; RATE COEFFICIENTS; IONS; ELEMENTS; FE
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-15782 (URN)10.1088/0031-8949/2011/T144/014035 (DOI)000291795900036 ()2-s2.0-80051697933 (Scopus ID)
Konferanse
Conference: 15th International Conference on the Physics of Highly Charged Ions, HCI2010 Location: Fudan Univ, Shanghai, PEOPLES R CHINA Date: AUG 29-SEP 03, 2010
Tilgjengelig fra: 2012-01-26 Laget: 2012-01-26 Sist oppdatert: 2012-08-14bibliografisk kontrollert
Orban, I., Lindroth, E., Glans, P. & Schuch, R. (2007). Spectroscopic study of doubly excited states in Mg-like Si using dielectronic recombination. Journal of Physics B: Atomic, Molecular and Optical Physics, 40(5), 1063-1080
Åpne denne publikasjonen i ny fane eller vindu >>Spectroscopic study of doubly excited states in Mg-like Si using dielectronic recombination
2007 (engelsk)Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, nr 5, s. 1063-1080Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present calculated and experimentally derived electron-ion recombination rate coefficients for Na-like Si IV, recombining into Mg-like Si III, and provide accurate spectroscopic data for doubly excited states located above the ionization threshold of Si III. The experimental recombination rate coefficients were measured in a merged-beam-type experiment at the heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm. Changing the electron-ion relative energy from 0 to 20 eV we covered the energy region from the first to the third ionization threshold. We find that even for the low-charged Si2+ ion, a relativistic many-body perturbation theory calculation is necessary, to describe the recombination rate coefficients in the low-energy region, up to 1.5 eV, satisfactorily. Doubly excited states, forbidden to form in LS coupling, are responsible for the most prominent dielectronic recombination resonances at low energies and contribute with 40% to the strength. Several wide resonances give rise to a plateau-like formation in the recombination spectrum. A broader energy range, up to 6.7 eV, was covered with a non-relativistic many-body calculation. This range contains, in addition to 3pnl resonances, several resonances of the type 3dnl, with the LS-forbidden 3d(2) F-3 states giving rise to a strong, isolated peak at 2.976 eV. The NIST database lists eleven doubly excited states of Si III with energy positions deviating considerably from our determination. Since the listed lines are also not fully matching those with the largest fluorescence yields it must be concluded that they are misidentified.

Emneord
ENERGY-LEVELS, IONS, RESONANCES, SPECTRUM, PHOTOIONIZATION, COEFFICIENTS, HELIUM, ARGON
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-4221 (URN)10.1088/0953-4075/40/5/018 (DOI)000244584800021 ()2-s2.0-33947593187 (Scopus ID)4952 (Lokal ID)4952 (Arkivnummer)4952 (OAI)
Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Orban, I., Glans, P., Altun, Z., Lindroth, E., Källberg, A. & Schuch, R. (2006). Determination of the recombination rate coefficients for Na-like Si IV forming Mg-like Si III. Astronomy and Astrophysics, 459(1), 291-296
Åpne denne publikasjonen i ny fane eller vindu >>Determination of the recombination rate coefficients for Na-like Si IV forming Mg-like Si III
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2006 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 459, nr 1, s. 291-296Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Aims. Absolute, total recombination rate coefficients for Si IV were determined using the CRYRING heavy-ion storage ring. Calculated rate coefficients were used to estimate recombination into states that could not be detected in the experiment because of field ionization. Total, as well as separate, radiative and dielectronic plasma recombination rate coefficients were determined. Methods. Stored ions were merged with an expanded electron beam in the electron cooler section of the storage ring. Recombined ions were separated from the stored ion beam in the first dipole magnet after the electron cooler and were detected with unity efficiency. The absolute radiative and dielectronic recombination rate coefficients were obtained over a center-of-mass energy range of 0-20 eV, covering Δ n = 0 core excitations up to the 3s → 3d series limit. The results of an intermediate coupling AUTOSTRUCTURE calculation were compared with the experiment. The theoretical results were also used to estimate the contribution to dielectronic recombination by high Rydberg states, which were not detected because of field ionization. The spectra were convoluted with Maxwell-Boltzmann energy distributions in the 103-10 6 K temperature range. Results. The resulting plasma recombination rate coefficients are presented and compared with theoretical results frequently used for plasma modeling. In the 103-104 K range, a significant underestimation of the calculated dielectronic recombination plasma rate coefficients was observed. Above 3 × 104 K, the agreement between our dielectronic recombination plasma rate coefficients and two of the previously published rate coefficients is better than 20%. Conclusions. The observed differences between the experimental and calculated recombination rate coefficients at low temperatures reflect the need for benchmarking experiments. Our experimentally-derived rate coefficients can guide the development of better theoretical models and lead to more accurately-calculated rate coefficients.

Emneord
Atomic data, Atomic processes, Plasmas
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-3845 (URN)10.1051/0004-6361:20054660 (DOI)000241789100033 ()2-s2.0-33750686014 (Scopus ID)4103 (Lokal ID)4103 (Arkivnummer)4103 (OAI)
Merknad

VR-Physics

Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Fogle, M., Badnell, N., Glans, P., Loch, S., Madzunkov, S., Abdel-Naby, S. .., . . . Schuch, R. (2005). Electron-ion recombination of Be-like C, N, and O. Astronomy and Astrophysics, 442(2), 757-766
Åpne denne publikasjonen i ny fane eller vindu >>Electron-ion recombination of Be-like C, N, and O
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2005 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 442, nr 2, s. 757-766Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of N3+ and O4+. Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of O4+, the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.

Emneord
atomic -- molecular and nuclear data
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-3452 (URN)10.1051/0004-6361:20040559 (DOI)000232404400041 ()3501 (Lokal ID)3501 (Arkivnummer)3501 (OAI)
Merknad
VR-PhysicsTilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Böhm, S., Müller, A., Schippers, S., Shi, W., Fogle, M., Glans, P., . . . Danared, H. (2005). Experimental NV and NeVIII low-temperature dielectronic recombination rate coefficients. Astronomy & Astrophysics, 437(3), 1151-1157
Åpne denne publikasjonen i ny fane eller vindu >>Experimental NV and NeVIII low-temperature dielectronic recombination rate coefficients
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2005 (engelsk)Inngår i: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 437, nr 3, s. 1151-1157Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The dielectronic recombination rate coefficients of Nv and Ne viii ions have been measured at a heavy-ion storage ring. The investigated energy ranges covered all dielectronic recombination resonances attached to 2s -> 2p (delta_n = 0) core excitations. The rate coefficients in a plasma are derived and parameterized by using a convenient fit formula. The experimentally derived rate coefficients are compared with theoretical data by Colgan et al. (2004, A&A, 417, 1183) and Nahar & Pradhan (1997, ApJ, 111, 339) as well as with the recommended rate coefficients by Mazzotta et al. (1998, A&A, 133, 403). The data of Colgan et al. and Nahar & Pradhan reproduce the experiment very well over the temperature ranges where Nv and Ne viii are expected to exist in photoionized as well as in collisionally ionized plasmas. In contrast the recommendation of Mazzotta et al. agrees with the experimental rate coefficient only in the collisionally ionized temperature range. At lower temperatures it deviates from the measured rate coefficient by orders of magnitude. In addition the influence of external electric fields with field strengths up to 1300 V/cm on the dielectronic recombination rate coefficient has been investigated.

HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-3156 (URN)3092 (Lokal ID)3092 (Arkivnummer)3092 (OAI)
Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2011-01-10bibliografisk kontrollert
Loch, S., Witthoeft, M., Pindzola, M., Bray, I., Fursa, D., Fogle, M., . . . Griffin, D. (2005). Influence of long-lived metastable levels on the electron-impact single ionization of C2+. Physical Review A. Atomic, Molecular, and Optical Physics, 71(1), 012716-1
Åpne denne publikasjonen i ny fane eller vindu >>Influence of long-lived metastable levels on the electron-impact single ionization of C2+
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2005 (engelsk)Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 71, nr 1, s. 012716-1Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A joint theoretical and experimental investigation is made of the influence of long-lived metastable levels on the electron-impact single ionization of C2+. It is expected that our electron cyclotron resonance ion source produces a beam with 40% of the C2+ ions in the 1s(2)2s(2) S-1(0) ground level and 60% in the 1s(2)2s2p P-3(0,2) excited levels. The comparison of nonperturbative close-coupling calculations with previous single-pass crossed beams and with our multiple-pass storage-ring measurements for the electron-impact ionization of C2+ is consistent with the predicted large metastable fraction. Reasonable agreement is found between the present time-dependent close-coupling, R-matrix with pseudostates, and converged-close-coupling ionization cross-section calculations for the ground and first excited configurations and experimental measurement, assuming a 60% metastable fraction in the ion beam. Distorted-wave calculations are found to overestimate the ionization cross section from both the ground and metastable terms, compared with nonperturbative calculations, resulting in an overestimation of the resultant total cross section when compared with experiment. It is clear that collisional-radiative modeling of the evolution of atomic plasmas through the Be-like ionization stage will need to take into account the role of both ground and metastable levels.

Emneord
CLOSE-COUPLING CALCULATIONS, BE-LIKE IONS, R-MATRIX, HYDROGEN SCATTERING, CROSS-SECTIONS, DIELECTRONIC RECOMBINATION, LI-LIKE, EXCITATION, ATOMS, STATE
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-3155 (URN)10.1103/PhysRevA.71.012716 (DOI)000227283300089 ()3091 (Lokal ID)3091 (Arkivnummer)3091 (OAI)
Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Glans, P., Fogle, M., Madzunkov, S., Tokman, M., Nikolic, D., Mohamed, T., . . . Schuch, R. (2004). Dielectronic recombination used as a tool for spectroscopic studies of highly charged ions. Physica scripta. T, T110, 212-215
Åpne denne publikasjonen i ny fane eller vindu >>Dielectronic recombination used as a tool for spectroscopic studies of highly charged ions
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2004 (engelsk)Inngår i: Physica scripta. T, ISSN 0281-1847, Vol. T110, s. 212-215Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Systematic studies of electron-ion recombination for Li-like, Na-like, and Cu-like ions have been made during the last few years at the CRYRING facility. The main purpose has been to measure recombination spectra with such high resolution and accuracy that stringent tests of advanced atomic calculations of doubly excited states can be made. From the comparison with theory it is possible to obtain energy positions, as well as radiative and nonradiative decay rates for the doubly excited states. In addition, for heavy, highly charged ions it is possible to deduce radiative corrections for energy splittings with very high accuracy.

Emneord
Recombination
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-2307 (URN)10.1238/Physica.Topical.110a00212 (DOI)000204271600035 ()2-s2.0-33846482891 (Scopus ID)1521 (Lokal ID)1521 (Arkivnummer)1521 (OAI)
Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Böhm, S., Schippers, S., Shi, W., Muller, A., Djuric, N., Dunn, G., . . . Badnell, N. (2003). Enhancement of dielectronic recombination by external electromagnetic fields. Hyperfine Interactions, 146-147(1-4), 23-27
Åpne denne publikasjonen i ny fane eller vindu >>Enhancement of dielectronic recombination by external electromagnetic fields
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2003 (engelsk)Inngår i: Hyperfine Interactions, ISSN 0304-3843, Vol. 146-147, nr 1-4, s. 23-27Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The enhancement of the dielectronic recombination rate of lithiumlike Ne7+ and O5+ ions by external electromagnetic fields has been measured at the storage ring CRYRING. The energy range covered all 1s(2)2pnl dielectronic recombination resonances attached to the 2s --> 2p core excitation. Electric fields up to 1436 V/cm were applied in the Ne7+ experiment and the saturation of the enhancement with increasing electric field could clearly be seen. In the O5+ experiment the enhancement was studied as a function of the Rydberg quantum number n.

Emneord
dielectronic recombination enhancement
HSV kategori
Identifikatorer
urn:nbn:se:miun:diva-2134 (URN)1215 (Lokal ID)1215 (Arkivnummer)1215 (OAI)
Tilgjengelig fra: 2008-09-30 Laget: 2008-09-30 Sist oppdatert: 2012-02-12bibliografisk kontrollert
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