Rotational Band Structure Research Articles

Jet-cooled ethylene cavity ring-down spectroscopy between 5880 and 6200 cm−1

Absorption spectra of jet-cooled ethylene (ethene, C2H4) are recorded at three different rotational temperatures (6/8 K, 12 K, 38 K) using cavity ring-down spectroscopy (CRDS) in the 5880–6200 cm−1 spectral region. Rotational cooling is used to determine the various vibrational band centers by simplifying drastically the rotational band structure. A line-by-line assignment, based on a direct comparison with the TheoReTS variational line list and a systematic use of lower state combination difference (LSCD), is performed. Experimental line lists including line position and line integrated absorption cross sections are drawn up. The 6/8 K, 12 K and 38 K spectra contain 668, 1553 and 1679 absorption lines respectively. Overall, 320 rovibrational lines are assigned across 20 interacting vibrational bands. Among the 20 vibrational cold bands identified in this work, 14 had never been observed before. Line intensities are in the range of 10−24 - 10−20 cm/molecule. A direct comparison between our work and the TheoReTS and ExoMol theoretical line lists, as well as with the recent experimental work of Ben Fathallah et al. (2024) is provided.

Octupole deformation in 143,145,146Ba

Gamma rays emitted by fission fragments of 252Cf and measured using the Gammasphere array continue to give insight into neutron rich nuclei. Using our high statistics data, we have reexamined high-spin states and linking transitions associated with octupole correlations in 143,145,146Ba. This has been a region of interest, when it was proposed that near 145Ba there was a region of octupole deformation. In an even-A system, it is possible that rotational band structures are explainable by simplex quantum numbers, s=+1 and s=−1. The previous bands including octupole bands in 143,145,146Ba have been extended. The new s=i octupole bands in 145Ba and new s=−1 octupole bands in 146Ba have been identified. In addition, collective model analysis of energy displacement, rotational frequency and B(E1)/B(E2) ratios have been carried out. Evidence of the rotational consequences of octupole deformation in even-even and even-odd isotopes is given. These nuclei have trends as rotation stabilizes the vibrational degrees of freedom. The experimental results are in agreement with theoretical calculations using the interacting boson and boson-fermion models that are based on a universal nuclear energy density functional.

Structure of rotational bands in Rh109

Rotational bands in $^{109}\mathrm{Rh}$ are investigated in a simple model and in the interacting boson-fermion model. We have developed a solvable extended transitional Hamiltonian by adding a two-configuration mixing term. Results suggest that $^{109}\mathrm{Rh}$ is a good candidate for triaxiality and shape coexistence. Mixing between $3/{2}^{+}$ states with $K=1/2$ and 3/2 is found to be weak, as evidenced by the $E2$ strengths.

Low-, medium-, and high-spin states in the N=Z+1 nucleus Ga63

The fusion-evaporation reaction $^{28}\mathrm{Si}+^{40}\mathrm{Ca}$ at 122 MeV beam energy was used to populate excited states in the $N=Z+1$ nucleus $^{63}\mathrm{Ga}$. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array, the level scheme of $^{63}\mathrm{Ga}$ was extended by more than a factor of two in terms of number of $\ensuremath{\gamma}$-ray transitions and excited states, excitation energy $({E}_{x}>30\phantom{\rule{0.16em}{0ex}}\mathrm{MeV})$, and angular momentum $(I>30\phantom{\rule{0.16em}{0ex}}\ensuremath{\hbar})$. Nine regular sequences of states were newly established in the high-spin part of the level scheme. The majority of these rotational band structures could be connected to the previously known part of the level scheme by high-energy $\ensuremath{\gamma}$-ray transitions in the energy range ${E}_{\ensuremath{\gamma}}=4--6\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. Low-spin states were assessed by shell-model calculations. The high-spin rotational bands were interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

Triangular symmetry in cluster nuclei

In this contribution, we present evidence for the occurrence of triangular symmetry in cluster nuclei. We discuss the structure of rotational bands for 3α and 3α +1 configurations with triangular D 3h symmetry by exploiting the double group and study the application to 12 C and 13C. The structure of rotational bands can be used as a fingerprint of the underlying geometric configuration of α particles.

Rotational Temperature of AlO Molecule from Fourier Transform Spectrum of the 0-1 band of B2∑+ - X2∑+ System

Rotational structure of (0-1) bands of the B2∑+ - X2∑+ system of AlO molecule was recorded on Fourier Transform Spectrometer. Intensity distribution among the well-resolved rotational lines of R1 and R2 for each band was recorded and average rotational temperature calculated from these lines which is 1813 K.

He8 and Li9 cluster structures in light nuclei

The possibility of the $^8$He and $^{9}$Li clusters in atomic nuclei is discussed. Until now most of the clusters in the conventional models have been limited to the closures of the three-dimensional harmonic oscillators, such as $^4$He, $^{16}$O, and $^{40}$Ca. In the neutron-rich nuclei, however, the neutron to proton ratio is not unity, and it is worthwhile to think about more neutron-rich objects with $N>Z$ as the building blocks of cluster structures. Here the nuclei with the neutron number six, which is the subclosure of the $p_{3/2}$ subshell of the $jj$-coupling shell model, are assumed to be clusters, and thus we study the $^8$He and $^9$Li cluster structures in $^{16}$Be ($^8$He+$^8$He), $^{17}$B ($^8$He+$^9$Li), $^{18}$C ($^9$Li+$^9$Li), and $^{24}$C ($^8$He+$^8$He+$^8$He). Recent progress of the antisymmetrized quasi cluster model (AQCM) enables us to utilize $jj$-coupling shell model wave functions as the clusters rather easily. It is shown that the $^8$He+$^9$Li and $^9$Li+$^9$Li cluster configurations cover the lowest shell-model states of $^{17}$B and $^{18}$C, respectively. To predict the cluster states with large relative distances, we increase the expectation value of the principal quantum numbers by adding the nodes to the lowest states under the condition that the total angular momentum is unchanged (equal to $J^\pi =0$). As a result, developed cluster states are obtained around the corresponding threshold energies. The rotational band structure of $^{24}$C, which reflect the symmetry of equilateral triangular configuration ($D_{3h}$ symmetry) of three $^8$He clusters, also appears around the threshold energy.

Observation of signature partner bands in Sb117

Rotational band structures and low-lying single-particle levels in $^{117}\mathrm{Sb}$ have been populated using reaction $^{115}\mathrm{In}(\ensuremath{\alpha}$, $2n)^{117}\mathrm{Sb}$ at a beam energy of 28 MeV and investigated using $\ensuremath{\gamma}$-ray spectroscopic techniques. The existing level scheme has been extended with the observation of 31 new transitions. The signature partner of the band structure based on the configuration of $\ensuremath{\pi}{g}_{7/2}\phantom{\rule{4pt}{0ex}}\ensuremath{\bigotimes}\phantom{\rule{4pt}{0ex}}2\mathrm{p}\text{\ensuremath{-}}2\mathrm{h}$ of the $^{116}\mathrm{Sn}$ core has been established in $^{117}\mathrm{Sb}$ for the first time. Several single-particle nonyrast transitions connecting to various band structures have also been identified. Measurements of the DCO ratios, polarization asymmetry and angular distribution of the observed $\ensuremath{\gamma}$ rays have been carried out to assign the spin-parities to the levels of all the band structures and the low-lying single-particle states, populated in the present work. The spin-parities are also determined for the states of the two previously unassigned bands. The lower-spin structures have been interpreted on the basis of large-scale shell-model calculations using OXBASH. Particle Rotor Model (PRM) calculations have been carried out to explain the large signature splitting of the observed signature partner bands.

New bands of deuterated nitrous acid (DONO) in the near-infrared using FT-IBBCEAS

The first measurements of near-infrared bands of deuterated nitrous acid (DONO) are presented. The measurements were made using Fourier-Transform Incoherent Broad-Band Cavity-Enhanced Absorption Spectroscopy (FT-IBBCEAS) in the 5800–7800 cm−1 region. Two bands of trans-DONO centred at 6212.029 and 7692.496 cm−1 were observed and assigned to the 2ν1+ν3 combination and 3ν1 overtone vibrations, respectively. Their rotational band structure was satisfactorily reproduced using PGOPHER. For cis-DONO the 3ν1 band was observed at ~7302.5 cm−1. In addition, new bands centred at 6142.5 cm−1 and 7607.6 cm−1 were quite confidently assigned to the 2ν1+ν3 and 3ν1 vibrations of deuterated nitric acid, DNO3, respectively.

Microscopic insight into the quasi-particle structure of odd-mass terbium isotopes

The present work has been focussed on the application of Projected Shell Model to study the negative parity rotational band structure up to the high spin states of the neutron-rich odd mass Terbium isotopes with neutron numbers ranging from 90 to 98. The structure evolution in these nuclei has been made on the basis of various nuclear structure properties like energy spectra, transition energies, wave functions and electromagnetic transition probabilities (B(E2) and B(M1)). Besides, the occurrence of back bending has also been reported in the present work.

Microsolvation of porphine molecules in superfluid helium nanodroplets as revealed by optical line shape at the electronic origin.

We investigate the line shape at the electronic origin of single porphine molecules doped into superfluid helium droplets as a function of the droplet size. Helium droplets comprised of less than 105 atoms are generated from an expansion of gaseous helium, while droplets with more than 105 atoms originate from liquid helium. In contrast to our recent study on phthalocyanine, porphine is found to exhibit a solvent shift to the blue with respect to the gas-phase resonance frequency as well as a multiplet splitting. A comparison of the helium-induced features of phthalocyanine and porphine with those obtained in similar studies on tetracene and pentacene reveals that these occur chiefly as two kinds of excitations distinguished by their linewidths and their dependence on the droplet size. Moreover, at quasi-bulk conditions achieved with droplets in excess of 106 helium atoms, none of these four dopant species yields an optical spectrum that can be assigned to a plausible rotational band structure.

Resonant spectra of multipole-bound anions

In multipole-bound anions, the excess electron is attached by a short-range multipole potential of a neutral molecule. Such anions are prototypical marginally-bound open quantum systems. In particular, around the critical multipole moment required to attach the valence electron, multipole-bound anions exhibit critical behavior associated with a transition from bound states dominated by low-$\ell$ partial waves to the electron continuum. In this work, multipole-bound anions are described using a nonadiabatic electron-plus-rotor model. The electron-molecule pseudo-potential is represented by a short-range multipole field with a Gaussian form-factor. The resulting coupled-channel Schr\"odinger equation is solved by means of the Berggren expansion method, in which the electron's wave function is decomposed into bound states, narrow resonances, and the non-resonant scattering continuum. We show that the Gaussian model predicts the critical transition at the detachment threshold. Resonant states, including bound states, decaying resonances, subthreshold resonances, and antibound states are studied, and exceptional points where two resonant states coalesce are predicted. We discuss the transition of rotational band structures around the threshold and study the effects of channel coupling on the decay width of resonant poles.

High Temperature Optical Spectra of Diatomic Molecules at Local Thermodynamic Equilibrium

In the paper, several theoretical approaches to the determination of the reduced absorption and emission coefficients under local thermodynamic equilibrium conditions were exposed and discussed. The full quantum-mechanical procedure based on the Fourier grid Hamiltonian method was numerically robust but time consuming. In that method, all transitions between the bound, free, and quasi-bound states were treated as bound–bound transitions. The semi-classical method assumed continuous energies of ro-vibrational states, so it did not give the ro-vibrational structure of the molecular bands. That approach neglected the effects of turning points but agreed with the averaged-out quantum-mechanical spectra and it was computer time efficient. In the semi-quantum approximation, summing over the rotational quantum number J was done analytically using the classical Franck–Condon principle and the stationary–phase approximation and its consumption of computer time was lower by a few orders of magnitude than the case of the full quantum-mechanical approach. The approximation described well the vibrational but not the rotational structure of the molecular bands. All the above methods were compared and discussed in the case of a visible and near infrared spectrum of LiHe, Li2, and Cs2 molecules in the high temperature range.

Deformed band structures in neutron-rich Pm152–158 isotopes

High spin band structures of neutron-rich $^{152-158}$Pm isotopes have been obtained from the measurement of prompt $\gamma$-rays of isotopically identified fragments produced in fission of $^{238}$U+$^{9}$Be and detected using the VAMOS++ magnetic spectrometer and EXOGAM segmented Clover array at GANIL and also from the high statistics $\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$-$\gamma$ data from the spontaneous fission of $^{252}$Cf using Gammasphere. The excited states in $^{157}$Pm and those above the isomers in even-A Pm isotopes $^{152,154,156,158}$Pm have been identified for the first time. The spectroscopic information on the rotational band structures in odd-A Pm isotopes has been extended considerably to higher spins and the possibility of the presence of reflection asymmetric shapes is explored. The configuration assignments are based on the results of Cranked Relativistic Hartree-Bogoliubov calculations. From the systematics of bands in odd-A Pm isotopes and weak population of opposite parity bands, octupole deformed shapes in neutron rich Pm isotopes beyond $N=90$ seem unlikely to be present.

Rotational structure of odd-proton 103, 105, 107, 109, 111Tc isotopes

A systematic study of the yrast band structure for the neutron-rich odd-mass 103-111Tc nuclei is carried out using Projected Shell Model. The rotational band structure has been studied up to a maximum spin of $ 59/2^{+}$ . Excellent agreement with available experimental data for all isotopes is obtained. The energy spectra and electromagnetic transition strengths in terms of the configuration mixing of the angular-momentum projected multi-quasiparticle states are studied in detail. Signature splitting in the yrast rotational band is well described in the perspective of nuclear structure physics. The back-bending phenomenon is also well described for these nuclei in the present work.

A systematic study of band structure and electromagnetic properties of neutron rich odd mass Eu isotopes in the projected shell model framework

The positive and negative parity rotational band structure of the neutron rich odd mass Eu isotopes with neutron numbers ranging from 90 to 96 are investigated up to the high angular momentum. In the theoretical analysis of energy spectra, transition energies and electromagnetic transition probabilities we employ the projected shell model. The calculations successfully describe the formation of the ground and excited band structures from the single particle and multi quasiparticle configurations. Calculated excitation energy spectra, transition energies, exact quantum mechanically calculated B(E2) and B(M1) transition probabilities are compared with experimental data wherever available and a reasonably good agreement is obtained with the observed data. The change in deformation in the ground state band with the increase in angular momentum and the increase in neutron number has also been established.

Strongly coupled rotational band in Mg33

Author(s): Richard, AL; Crawford, HL; Fallon, P; Macchiavelli, AO; Bader, VM; Bazin, D; Bowry, M; Campbell, CM; Carpenter, MP; Clark, RM; Cromaz, M; Gade, A; Ideguchi, E; Iwasaki, H; Jones, MD; Langer, C; Lee, IY; Loelius, C; Lunderberg, E; Morse, C; Rissanen, J; Salathe, M; Smalley, D; Stroberg, SR; Weisshaar, D; Whitmore, K; Wiens, A; Williams, SJ; Wimmer, K; Yamamato, T | Abstract: The island of inversion at N≈20 for the neon, sodium, and magnesium isotopes has long been an area of interest both experimentally and theoretically due to the subtle competition between 0p-0h and np-nh configurations leading to deformed shapes. However, the presence of rotational band structures, which are fingerprints of deformed shapes, have only recently been observed in this region. In this work, we report on a measurement of the low-lying level structure of Mg33 populated by a two-stage projectile fragmentation reaction and studied with the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA). The experimental level energies, ground-state magnetic moment, intrinsic quadrupole moment, and γ-ray intensities show good agreement with the strong-coupling limit of a rotational model.

IMPACT OF TRANSFER PROCESSES OF LIQIUD CATHODE COMPONENTS ON PHYSICAL-CHEMICAL PARAMETERS OF ATMOSPHERIC PRESSURE DC DISCHARGE

Experimental data on glow discharge parameters of atmospheric pressure in air with cathodes from distilled water and water containing ions of potassium, sodium and copper (II) are obtained. Chlorides of the corresponding salts were used. The current range was 20-60 mA, and the solution concentrations were -0.1-0.4 mol/l. The cathode drops of the potential and the electric fields in the plasma are determined by the mobile anode method. With emission spectroscopy by modeling the unresolved rotational structure of the emission bands of the second positive system of nitrogen molecules, gas temperatures were found. On the basis of these data, the total concentrations of the particles, the reduced electric field strengths, were found. It is found that the increase in the discharge current leads to a decrease in the cathode drops of the potential, the strengths of the electric fields, and the reduced field strengths. At the same time, the temperature of the gas was practically independent on the discharge current and it was 1600 ± 150 K. By numerical solution of the Boltzmann equation for electrons, electron energy distribution functions, mean energies and electron concentrations and rate constants of the processes occurring under the action of electron impact were determined. An estimate is made of the contribution to the formation of charged particles in the plasma of ionization processes of metal atoms that appear in the gas phase as a result of non-equilibrium transfer from the liquid cathode. It is shown that for molar fractions of metal atoms of 10-4 and higher, ionization is completely determined by collisions of electrons with metal atoms, rather than with molecules of the main plasma-forming gas. It is also shown that discharges with cathodes containing salt solutions have smaller values of cathode potential drops.Forcitation:Kuletsan A.L., Shutov D.A., Rybkin V.V. Impact of transfer processes of liqiud cathode components on physical-chemical parameters of atmospheric pressure dc discharge. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 52-58.

Current and Future Tests of the Algebraic Cluster Model of12C

A new theoretical approach to clustering in the frame of the Algebraic Cluster Model (ACM) has been developed. It predicts, in12C, rotation-vibration structure with rotational bands of an oblate equilateral triangular symmetric spinning top with a D3h symmetry characterized by the sequence of states: 0+, 2+, 3−, 4±, 5− with a degenerate 4+ and 4− (parity doublet) states. Our newly measured state in12C allows the first study of rotation-vibration structure in12C. The newly measured 5− state and 4− states fit very well the predicted ground state rotational band structure with the predicted sequence of states: 0+, 2+, 3−, 4±, 5− with almost degenerate 4+ and 4− (parity doublet) states. Such a D3h symmetry is characteristic of triatomic molecules, but it is observed in the ground state rotational band of12C for the first time in a nucleus. We discuss predictions of the ACM of other rotation-vibration bands in12C such as the (0+) Hoyle band and the (1−) bending mode with prediction of (“missing 3− and 4−”) states that may shed new light on clustering in12C and light nuclei. In particular, the observation (or non observation) of the predicted (“missing”) states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha particles composing the Hoyle state at 7.6542 MeV in12C. We discuss proposed research programs at the Darmstadt S- DALINAC and at the newly constructed ELI-NP facility near Bucharest to test the predictions of the ACM in isotopes of carbon.

Geometric symmetries in light nuclei

The algebraic cluster model is is applied to study cluster states in the nuclei12C and16O. The observed level sequences can be understood in terms of the underlying discrete symmetry that characterizes the geometrical configuration of the α-particles, i.e. an equilateral triangle for12C, and a regular tetrahedron for16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of α-particles.