Measurement of the population of the4 P 5/2-state in Ar15+ by cascading processes

The population of the⁴ P _5/2-state in Ar¹⁵⁺-ions by cascading processes was measured. The corrected lifetime is (0.55±0.04) ns and is in very good agreement with the theoretical value of 0.56 ns. At a specific beam energy of 1.4 MeV/u the lifetime of the³ P ₂-state of Ar¹⁶⁺ is not influenced by cascading processes and is (1.44±0.08) ns. The energies of the³ P ₂ →¹ S ₀- and⁴ P _5/2 →² S _1/2-transitions are (3127.2±0.5) and (3090.0±0.7) eV, respectively.     

High resolution spectroscopy of prompt and metastable decaying levels in highly ionized argon,especially of the metastable3 P 2-state of Ar16+ and the4 P 5/2-state of Ar15+

Besides the prompt x-ray emission of Ar-ions, the metastable decay of the heliumlike³ P ₂- and the lithiumlike⁴ P _5/2-levels of highly ionized Ar¹⁶⁺ and Ar¹⁵⁺ atoms has been observed in a foil-excited beam using a flat-crystal spectrometer. Due to the highx-ray energy resolution of the spectrometer the two³ P ₂ →¹ S ₀ and⁴ P _5/2 →² S _1/2 transitions could be resolved. The experiment yielded (3128 ±2) eV for the³P₂ → and (3091 ± 2)eV for the⁴ P _5/2 →² S _1/2 transition energy respectively. Using a time of flight technique the lifetimes of the³ P ₂- and the⁴ P _5/2-states were determined to be (1.44 ±0.09)ns and (0.66 ± 0.05) ns.     

Lifetime measurements of the3 P 2 and4 P 5 2/0 states in He- and Li-like titanium and chromium

Ti and Cr ions at specific energies of 3.6 MeV/N and 5.0 MeV/N have been excited by passing them through thinC foils. The emission ofK-x rays andK-Auger electrons have been investigated using a flat crystal spectrometer and an electrostatic cyclindrical mirror analyzer. The lifetimes of the (1s2p)³ P ₂ and (1s2s2p)⁴ P _5/2 states have been determined by applying the time-of-flight technique. The experimental resultsτ(Ti²⁰⁺,³ P ₂)=(404±40)ps,τ(Cr²²⁺,³ P ₂)=(215±35)ps,τ(Ti¹⁹⁺,⁴ P _5/2)=(236±12)ps, andτ(Cr²¹⁺,⁴ P _5/2)=(140±8)ps are compared with calculated lifetimes.     

Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+

In this note we present the first account of a study of metastable (unimolecular decay) and collision-induced dissociation of Ar₃+ cluster ions using an experimental setup consisting of a molecular beam-electron impact ion source and a double focussing (reversed Nier Johnson geometry) mass spectrometer. The existence of the following metastable decay processes (accessible by our sampling time window) could be demonstrated: Ar₃⁺* → Ar₂+ and Ar₃⁺* → Ar⁺. The processes were studied as a function of electron impact energy. The present results are of importance in order to provide some guidance for the development of appropriate theoretical models for the dissociation of cluster ions.     

Chemiluminescent GeCl4 + O2 + Ar/He/Reactions

A chemiluminescent flame was produced in the reaction between GeCl₄ and an excited mixture of argon or helium with oxygen. Spectra of the reaction products were recorded and studied. Relative populations of the products in analyzed electronic, vibrational and rotational states corresponded to different temperatures.     

Dissociation energies of the I(3/2g) and I(1/2g) states of Ar+ 2

Rotationally resolved pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of ⁴⁰Ar₂ and ³⁶Ar₂ have been recorded between 124650cm^?1 and 127 150cm^?1 following resonant two-photon excitation via the 0⁺ _u (v¹= 0) Rydberg state located below the Ar (¹S₀) + Ar?((3p)⁵4s′ [1/2]₁) dissociation limit. Four overlapping vibrational progressions were observed and attributed to transitions to the I(1/2u) u⁺ = 35–50, I(3/2g) u⁺ = 0–10, I(1/2g) v⁺ = 0–6 and I(3/2u) v⁺ = 0–2 vibronic states of Ar⁺ ₂. The vibrational quantum numbers of the ionic states were derived from an analysis of the isotopic shifts, and the dissociation energies of the I(3/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂:) = 1509.4 ± 1.2cm^?1) and the I(1/2g) (D⁺ ₀(⁴⁰Ar⁺ ₂) = 616.3 ± 1.2cm^?1) states were determined.     

Precision lifetime measurement of fine structure states in the NeI 2p53p configuration

The beam—gas-laser two-step excitation technique of a fast ion beam is used for precision measurements of atomic life-times. By observing the decay of the purely laser induced fluorescence radiation, the lifetimes of eight fine-structure levels 2p₂ to 2p₉ in the NeI 2p⁵3p configuration were measured with total standard deviations of 0.2 to 0.5%.     

3 to 15 keV Ar+ induced Auger electron emission from Si and Ar

Ar⁺ induced Auger electrons from Si and Ar were investigated at bombardment energies between 3–15 keV and target currents of a few μA. The Auger electron yields were compared with secondary ion yields of Si and Ar by simultaneous SIMS-AES measurements. In the ion induced Auger spectra of Si five Auger peaks and in the Ar spectra three Auger peaks were observed. The ion induced Auger electron yield of Si and Ar were found to be strongly dependent upon the primary ion energy. “Bulk like” and “atomic like” Auger transitions of ion induced Auger electrons of Si were observed.     

Probing electronic states of Ne2+ and Ar2+ by measuring kinetic-energy-release distributions

Dissociative decay of metastable, electronically excited neon and argon dimer ions produces fragment ions with strikingly dissimilar kinetic-energy-release distributions. The distributions have been modeled based on ab initio calculations of potential energy curves. The unusual bimodal distribution observed for dissociation of Ne2+ arises from competition between radiative and nonradiative decay of the long-lived II(1/2)(u) state. For Ar2+, however, electronic predissociation is insignificant.     

Core polarization and 5/2+ states in91Nb

The energies and spectroscopic factors ofJ ^π=5/2⁺ states of nucleus⁹¹Nb excited via a reaction transferring a proton to the 2d _5/2 orbit of⁹⁰Zr target state have been calculated. Effective two-body interaction used has been extracted from the experimentally observed two-body energies of (1g ₉ ^2/?1 (n) 2d _5/2(n)), (1g ₉ ^2/?1 (n) 1g _9/2(p)) and (1g _9/2(p)-2d _9/2(n)) multiplets in⁹⁰Zr,⁹⁰Nb and⁹²Nb nuclei respectively. Most of the calculated energies and the strengths ofJ ^π=5/2⁺ levels have reasonably good counterparts in the experimental spectrum, however the calculation shows about 17% strength lying at 6.8 MeV, without having a confirmed counterpart in the observed level scheme. The reduced transition strengthsB(M1) forM l transitions from 5/2^? T>(11/2) state to the various components of 5/2⁺ T<(=9/2) state have also been reported; but the corresponding experimental values are not available. The main feature of the reduced transition strengths is that theM1 transition to the state at 3.69 MeV is inhibited whereas that to the state at 6.79 MeV is enhanced, the relevant core-configuration, interfering destructively in the former case and constructively in the latter.     

Spiked and screened oscillatorsV(r) =Ar 2 +B/r 2 +C/r 4 +D/r 6 +F/(1 +Gr)2 and their elementary bound states

We show that the complicated superpositionsV(r) of several important phenomenological forces may still lead to an elementary form of doublets of bound states under transparent algebraic constraints. Constructively, we show how (and when) the constrained couplings preserve compatibility with the physical regularity of wavefunctions.     

Photoionization cross section of Xe+ ion in the pure 5p5 2P3/2 ground level

Coupling an ion trap with synchrotron radiation is shown here to be a powerful approach to measure photoionization cross sections on ionic species relaxed in their ground state. The photoionization efficiency curve of Xe+ ions stored in a Fourier transform ion cyclotron resonance ion trap was recorded at ELETTRA in the 20-23 eV photon energy range. Absolute cross sections were derived by comparison of the photoionization yield of Xe+ with measurements from the ASTRID merged-beam experiment. Multiconfiguration Dirac-Fock calculations were performed for the interpretation of these new data.     

Measurement of the lifetime of the first 2+ state in 124Ba

The lifetime of the first 2⁺ state in the nucleus ¹²⁴Ba has been measured by γ-γ coincidence recoil-distance Doppler shift method. The ¹⁰⁹Ag(¹⁹F, 4n)¹²⁴Ba reaction at a beam energy of 75 MeV was employed to populate excited states in ¹²⁴Ba. The mean lifetime was determined to be 275(12) ps using the differential decay curve method. The value of B(E2;0₁ ⁺→ 2₁ ⁺) for ¹²⁴Ba deduced from the lifetime is in reasonable agreement with the prediction of the proton-neutron interacting boson model(IBM-2) without Pauli blocking effect. Received: 23 February 1998     

Measurement of the hyperfine structure splitting for the 4 and 52 P 1/2 states of sodium using radio-frequency spectroscopy

The hyperfine-structure splitting for the 4 and 5² P ^1/2 states of sodium was measured using step-wise laser excitation combined with rf-resonance techniques. The magnetic dipole interaction constants were found to be a(4² P _1/2)=30.4(5) MHz and a(5₂ P _1/2) =13.3(2) MHz. The results are compared with a theoretical calculation, taking polarization effects into account.