Magnetic moments for lithium quartet S states

The fully correlated calculations of the Zeeman g_J factors for the first three quartet S states of lithium are presented, including relativistic and radiative corrections of orders α², α² m/M, and α³. The isotope shifts in g_J are predicted precisely for various isotopes of lithium. Received 4 December 2000 and Received in final form 26 September 2001     

Observation of transitions between quartet levels of doubly excited Al10+

The line multiplet Al XI 1s2s2p 4P^o-1s2p^{2 4}P has been observed using beam-foil spectroscopy. The mean transition wavelength λ=(53.283±0.01) nm and three out of four finestructure intervals have been determined. The results are compared to recent theoretical calculations.     

Unbound excited states in C

The neutron-rich carbon isotopes ^19,17C have been investigated via proton inelastic scattering on a liquid hydrogen target at 70 MeV/nucleon. The invariant mass method in inverse kinematics was employed to reconstruct the energy spectrum, in which fast neutrons and charged fragments were detected in coincidence using a neutron hodoscope and a dipole magnet system. A peak has been observed with an excitation energy of 1.46(10) MeV in ¹⁹C, while three peaks with energies of 2.20(3), 3.05(3), and 6.13(9) MeV have been observed in ¹⁷C. Deduced cross sections are compared with microscopic DWBA calculations based on p-sd   shell model wave functions and modern nucleon–nucleus optical potentials. Jπ$J^{\pi }$ assignments are made for the four observed states as well as the ground states of both nuclei.     

Giant resonances on excited states

We derive modified RPA equations for small vibrations about excited states. The temperature dependence of collective excitations is examined. The formalism is applied to the ground state and the first excited state of ⁹⁰Zr in order to confirm a hypothesis which states that not only the ground state but every excited state of a nucleus has a giant resonance built upon it.     

Wavelength measurements in the quartet term system of doubly excited OVI and FVII

In the emission spectra of beam-foil excited oxygen and fluorine, it has been possible to assign lines to the quartet term systems of doubly excited three electron ions. A comparison with known spectra of singly excited four-electron systems turned out to be useful for line identification. The measured wavelengths are compared to theoretical predictions.     

Highly excited rovibrational states of HNC

The emission spectrum of HCN has been recorded at 1463 K using hot gas molecular emission (HOTGAME) spectroscopy in the wavenumber region of 2900–3500 cm⁻¹ with a resolution of 0.01 cm⁻¹. The dense emission spectrum was analyzed with the spectrum analysis software SyMath™ implemented in the Mathematica™ computer algebra system. This work reports the analysis of the band series up to v₂ = 8 and of the band series up to v₂ = 6.36 rovibronic (v₁, v₂, l, e/f, v₃) substates of HCN including all l = 0, 2, 4, 6, 8 sublevels of the highly excited bending combination mode have been characterized for the first time and for the 22 known vibrational sublevels it was possible to improve the existing spectroscopic constants substantially. 18 (v₁, v₂, l, v₃) vibrational sublevels are located for the first time relative to the 00⁰0 state. The analysis reported here includes rovibrational states up to very large rotational excitations of J = 60–80. For the combination states the rotational states have been determined up to J = 86 which corresponds to 7000 cm⁻¹ rotational excitation energy, this state is only 2000 cm⁻¹ below the isomerization barrier. It was possible to determine for the first time the L_v high order rotational constant for many states reported in this work.     

Singly excited states of neutral potassium

Energy levels, oscillator strengths and photoionization cross-sections are calculated. Superposition of configuration method is applied to study ground-state resonant singly excited electron transitions of neutral potassium including the near continuum ionization threshold. Orbitals are generated using scaled angular momentum-dependent Thomas-Fermi-Dirac-Amaldi potentials.     

Structure of excited states in Se-isotopes

Energy systematics of the anomalously low-lying excited 0⁺ states and the systematic behaviour of theB(E2: 0⁺→2 ₁ ⁺ ) values in Se-isotopes are investigated by taking the important effect of mutual interplay between dynamical pairing and quadrupole correlations into account.     

Formation of antihydrogen in excited states

A two state approximation method used by author earlier for positron–hydrogen charge-exchange process is used to compute antihydrogen formation cross-sections in excited states. Cross-section results are compared with other existing calculations in the energy range 30 keV–500 keV. Total cross-section results for antihydrogen formation are also being reported.     

Lowest excited states of 2-aminopurine

Absorption and fluorescene spectra and quantum yields of emission over a wide range of pH and solvent polarity were measured for 2-aminopurine and 2-dimethylaminopurine. An increase in dipole moment and a rise of pK values for N₁(N₃) ring atom protonation in the excited state were demonstrated. Thus, the lowest excited singlet state shows partially the (1, a_π¹) configuration. The polarization, lifetimes and the phosphorescence-to-fluorescence ratios indicate that spin-orbit coupling of ¹(n, π¹) and ¹(1, a_π¹) with the lowest triplet state is the main source of phosphorescence intensity. The matrix element of spin-orbit coupling of ¹(n, π¹) to the T₁ state is about 33 times larger than that of ¹(1, a_π¹). The temperature- dependent process of 2-aminopurine fluorescence quenching in either is presumably due to the thermal population of the second excited triplets state of (n, π¹) configuration, which can approximately be located at 370 cm^-1 above the lowest (1, a_π¹) singlet.     

Investigation of22Na excited states

Fourteen²¹Ne(p, γ)²²Na resonances have been observed in the rangeE _p =300–1,300 keV. Theγ-decay of all these resonances has been investigated by means of a 38 cm³ Ge(Li) detector. Energies and branching ratios of several bound states have been determined. TheQ-value was determined as 6,738.5±1.7 keV. Lifetimes of seven states were determined with the Doppler-shift attenuation method. The observed upper limit (τ _m ≦4 fs) of the lifetime for the 4,071 keV state, regarded as the analogue of the third excited state in²²Ne, and the transition observed from this state to the 1,528 keV state do not support the proposed rotational band structure of the²²Na low-lying states.     

Acceptor excited states in indium phosphide

Selective donon-acceptor pair luminescence and luminescence excitation spectra reveal acceptor excitations to all excited states of principal quantum number 2, odd as well as even parity. These transition energies are independent of the D-A pair separation R for sufficiently large R and are then identical to those on isolated acceptors. However, they decrease significantly at small R and some splittings are revealed in our measurements on a bulk grown crystal in which the most common contaminant acceptor Zn is dominant. The p state transition energies are used together with the known ionization energy of the Zn acceptor to derive valence band parameters for InP according to the theory of Baldereschi and Lipari. We find γ₁ = 5.6 ± 0.7, γ₂ = 2.0 ± 0.3, γ₃ = 2.4 ± 0.3, where γ₁ is adjusted to fit the cyclotron resonance data of Leotin et al. Some reservations concerning the completeness of this theory are acknowledge. Information on the s acceptor excited state is consistent with that obtained from acceptor bound exciton “two-hole” satellites for this remarkable quality bulk crystal.     

Condensate of excited states in magnesium

The results of theoretical study of the condensate of excited states in magnesium are reported. Excitations are described in the framework of the Hartree-Fock method taking into account energy level widths. It is shown that conditions for the emergence of condensed excited states are created in the optical range of atomic excitation energies. In the Mg₂ system, such conditions are created for any (indefinitely small) excitation fields in the optical energy range. The weaker the external field, the longer the lifetime and the shallower the potential well for the condensate of excitations. Most stable excitations in Mg₂ were detected at atomic spacings on the order of 9 Bohr radii.     

Variational method for excited atomic states

An analysis is presented of the extremum properties of energy functionals for the excited states of many-electron systems, in particular, atoms, in the case when there exist low-lying states of the same symmetry as the excited state under consideration. Two theorems are proved concerning the relationship between the upper bound on the eigenvalues corresponding to the excited states and the extremum properties of the energy functional determined by variational test functions which depend on parameters. In this context, different variants of the one-electron approximation used in the excited-state calculations are considered: the method of obtaining self-consistent solutions with one-electron functions orthogonal within the configurations (the Hartree-Fock method for configurations); the frozen atomic core approximation for the excited configuration; the method of nonorthogonal orbitals in the excited configuration; and the approximation of the frozen ionic core. Cases are identified and reasons given for the possible collapse of the excited state energy level to an unjustifiably low value of the energy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 18–33, August, 1990.     

Dynamics of electron excitation of low-energy quartet states of the potassium atom

The electron excitation function for the lowest (3p ⁵3d4s)⁴ P autoionizing quartet level of the potassium atom is measured in the energy range from the threshold of the process to 102 eV at the energy resolution of 0.3 eV or better. The near-threshold energy region is studied in detail for the first time. The main processes that govern the dynamics of excitation of the low-lying quartet levels in the potassium atom are analyzed by comparing these data with the excitation functions obtained earlier for the (3p ⁵4s4p)⁴ S and (3p ⁵4s4p)⁴ D levels. In particular, the resonances of negative ions in the near-threshold energy region are shown to play a dominant role, as well as to significantly affect the efficiency of the cascade transitions from higher-lying quartet levels.     

Dynamic hyperpolarizabilities of excited states of hydrogen

On the basis of the generalized Sturm expansion of the radial part of the Coulomb Green function, a computational method is proposed and numerical results are presented for the dynamic hyperpolarizability γ and the corrections E ⁽⁴⁾ (quadratic in the light intensity) to the quasi-energy of the ground and excited states of hydrogen with principal quantum numbers n≤5 in a monochromatic light field. In this approach, the problem is reduced to the summation of well-convergent double series of the hypergeometric kind, which ensures reliable numerical results both for states with a large n, and in a wide range of field frequencies ω, including the above-threshold frequency range of ?ω?|E _n | (|E _n | is the ionization potential of the state |nlm〉 under investigation). We consider the frequency dependence of γ and E ⁽⁴⁾, their differences for the cases of linear and circular polarizations of the field, and the relation between their real and imaginary parts, which determine the laser field-induced corrections to the position and width of energy levels. For n=5, the significant role of mixing the |nlm〉 states with different values of l by a laser field in the region of resonances on intermediate bound states is demonstrated. The linear (in intensity) corrections to the photoionization cross section for excited states are analyzed and the threshold intensity corresponding to the onset of atomic level stabilization is estimated for a number of states with n=3 and n=5.