A study of the rotational side-bands in 162Dy

Rotational side-bands in ¹⁶²Dy have been studied using the ¹⁶⁰Gd(α, 2nγ)¹⁶²Dy reaction. Seven side-bands are observed, with K^π = 2⁺, 2^?, (0)^?, 0⁺, 5^?, 4⁺ and (6^?). Four of these bands have collective structure at low spin: the K^π = 2⁺γ-vibrational band, the K^π = 0⁺β-vibrational band, and the K^π = 2^? and (0)^? octupole vibrational bands. Of the remaining bands, the 4⁺ band is deformation coupled while the 5^? and (6^?) bands are rotation-aligned. Several bandcrossings are observed in this nucleus. The β and γ-bands are crossed at $\text{I = 6}\text{h}\text{?}\text{and}\text{12}\text{h}\text{?}$, respectively, by a highly aligned ($\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$)² S-band; extrapolation of this S-band to higher spin suggests that it crosses the g.s.b. between $\text{I = 18}\text{h}\text{?}\text{and}\text{20}\text{h}\text{?}$. The 2^? octupole band is crossed by the 5^? band at $\text{I = 9}\text{h}\text{?}$ and again by the (6^?) band at $\text{I = 12}\text{h}\text{?}$. The latter bandcrossings are discussed in terms of two-quasiparticle plus rotor calculations.     

Resonant interaction of acceptor states and optical phonons in silicon

The resonance broadening of line 2 in the excitation spectrum of gallium acceptors in silicon due to near coincidence of its energy with that of the zone center optical phonons, $\text{h}\text{?}$ω₀, has been confirmed under significantly improved experimental conditions. An additional feature labeled X and line 2 are interpreted as mixed excitations of the bound-hole and the optical phonon. Under uniaxial stress, the stress induced components of line 2 which approach $\text{h}\text{?}$ω₀ become more phonon-like and get “pinned” while the components of X become bound-hole-like as they recede from $\text{h}\text{?}$ω₀, and exhibit a striking increase in intensity.     

The systematics of h112 proton alignment in 157, 158, 159Er

Rotational bands have been observed in ^{157, 158, 159}Er to very high spin ($\text{J ～ 41}\text{h}\text{?}$). Upbends are found, due to the alignment of two h_{$\text{11}\text{2}$} protons at $\text{0.40 ?}\text{h}\text{?}\text{ω ? 0.46}\text{MeV}$ in all bands. A systematic shift with neutron number of the band-crossing frequency is observed and is related to a change in quadrupole deformation ?₂.     

Crossing relations for deep-inelastic and annihilation processes

We calculate in a model field theory [φ³]_σ the structure functions $\text{F}\text{?}\text{(ω), F(ω)}$ for the processes e⁺+e^?→h+X and e^?+h→e^?+X in the next to leading logarithm approximation. We find that $\text{F}\text{(ω) and F(ω)}$ satisfy the analytic continuation relation but not the Gribov-Lipatov reciprocity relation.     

The longitudinal magnetophonon effect in semiconductors containing magnetic impurities

The dependence of longitudinal magnetoresistance on magnetic field in semiconductors containing magnetic impurities is investigated theoretically. The calculation takes into account the scattering of electrons on magnetic impurities and on optical phonons. The inelastic optical phonon scattering itself is responsible for magnetophonon oscillations of the magnetoresistance, the extremes of these oscillations occuring when energy distance between Landau levels is equal to the energy of optical phonon, $\text{h}\text{?}$ω₀. The scattering on magnetic impurities may lead to spin flip electronic transitions. The spin flip electronic transitions manifest themselves as additional minima on the oscillatory picture of magnetoresistance. These new minima occur when the energy separation between spin-split Landau levels is equal to $\text{h}\text{?}$ω₀.     

Symplectic shell-model calculations for 20Ne with horizontal configuration mixing

The symplectie shell model, which incorporates vertical $\text{(2n}\text{h}\text{?}\text{ω; n = 1, 2…)}$ major shell configuration mixing as dictated by a quadrupole interaction, is augmented with horizontal (0?ω) mixing induced by realistic single-particle energies and a monopole-pairing interaction. The excitation spectrum and B(E2) rates of the ²⁰Ne ground band are accurately reproduced without the use of an effective charge. The degree of horizontal and vertical mixing is found to be on the order of 20% in the ground state and up to as much as 50% for the 8⁺ level.     

Far infrared absorption in bulk amorphous red phosphorous

Far infrared absorption measurements have been performed above 30 cm^?1 in bulk amorphous red P at 300 K. A number of low frequency spectral features are observed that are not present in the corresponding bulk amorphous As spectrum. Deep minima observed at 163 and 320 cm^?1 in α(ω) and in the Raman spectra suggest that the phonon density of states is essentially divided into 3 bands. A calculation of the mean effective charge of the bands indicates weak coupling to the lowest frequency band. A comparison with the results in a-As suggests a less rapid frequency variation in the infrared coupling parameter at low frequencies in a-$\text{P}$.     

Inelastische streuung langsamer elektronen an quecksilberoberflächen

We have measured the energy distribution of electrons inelastically scattered from extremely pure solid mercury surfaces. The primary electrons are generated by photoemission. The energy distribution curves of the scattered electrons exhibit two loss maxima which we interpret as plasma losses. We obtain for the value of the surface plasmon $\text{h}\text{?}\text{ω}{}_{\mathrm{<mtext>s</mtext>}}\text{=6.1±0.15}\text{eV}$ and for the volume plasmon $\text{h}\text{?}\text{ω}{}_{\mathrm{<mtext>p</mtext>}}\text{=7.9±0.3}\text{eV}$.     

Spin and lifetime of the ω− hyperon

A total of 101 ω^? decays have been found in K^?p interactions at 10 and $\text{16 GeV}\text{c}$. The decay angular distribution has been fitted under the assumptions that the ω^? has spin either $\text{1}\text{2}\text{or}\text{3}\text{2}$. It has been found that the probability of isotropy (spin$\text{1}\text{2}\text{)}$ is less than one in a thousand, whereas the probability for spin $\text{3}\text{2}$ is about 70%. Thus, we exclude the spin $\text{1}\text{2}$ assignment. The lifetime of the ω^? is found to be (1.41_?0.24^+0.15) × 10^?10s, in agreement with our earlier result based on about $\text{1}\text{5}$ of the present sample.     

On the derivation of effective interactions by matrix diagonalization methods

A technique is developed which in certain cases allows the derivation of a completely linked two body effective interaction for two particles beyond a closed shell using matrix diagonalization methods. In particular this applies to a space consisting of 0 and $\text{2}\text{h}\text{?}\text{ω}$ excitations.     

Repeated zones and Mahan cones in the angular dependence of photoemission

The intensity of photoemission from the Ta-derived d states in the layer compound 1T-TaS₂ has been measured as a function of both polar and azimuthal angle of emission at the photon energy $\text{h}\text{?}\text{ω=21.2}\text{eV}$. The light source was a high intensity He resonance lamp employing an aluminum window in place of the more conventional differentially pumped capillary system. The azimuthal dependence of the d emission displays three kinds of lobes which we refer to as “heads, chins and ears”. The heads and chins are oriented along directions close to the bifurcated lobes observed previously at $\text{h}\text{?}\text{ω=10.2}\text{eV}$. The ear lobes, however, are oriented quite differently and appear only at high polar angles, corresponding to larger relative values of the parallel wavevector. The results can be understood in terms of a repeated zone scheme in which the ears and chins (not necessarily at the same polar angle) correspond to different Mahan cones of the same optical transitions.     

The quadrupole moments of the 5− states in 116Sn, 118Sn and 120Sn

The quadrupole interaction frequencies $\text{ω}{}_0\text{=}\text{3eQ}{}_1\text{V}{}_{\mathrm{zz}}\text{41(21-1)}\text{h}\text{?}$ in the 5^? state of ¹¹⁸Sn have been measured by time differential perturbed angular correlation technique in Sn, Sb and (95% Sn+5% Sb) environments. The ω₀ for ¹¹⁶Sn was determined in Sn environment only. With the help of the known electric field gradient ¹) of Sn in a Sn lattice the quadrupole moments have been deduced as $\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{118}\text{Sn}\text{) = ±0.10(4) b}\text{and}\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{116}\text{Sn}\text{) = ±0.165(60)}\text{b}$. These values together with the known²) quadrupole moment of the analogous 5^? state in ¹²⁰Sn are interpreted in terms of the pure single-particle model. The data exhibit the expected strong systematic variation of Q_I with the number of particles in the h_{$\text{11}\text{2}$}. subshell which is being filled with 1, 3 and 5 neutrons in ¹¹⁶Sn, ¹¹⁸Sn, and ¹²⁰Sn, respectively.     

Structure of high-spin states in 232Th, 234U and 236U

Multiple Coulomb excitation of ²³²Th, ²³⁴U and ²³⁶U by 5.3 $\text{MeV}\text{u}$²⁰⁸Pb ions has been studied using γ-ray spectroscopy. Excitation of ground-band levels is observed up to spin I^π = 26⁺ (tentatively 28 ⁺) in ²³²Th and ²³⁴U and I^π = 28⁺ (tentatively 30⁺)in ²³⁶U. High-spin levels of the K^π = 0^? octupole-vibrational bands are also observed in these nuclei. The measured transition energies between ground-band levels suggest that at $\text{I≈ 28}\text{h}\text{?}$ several units of angular momentum are carried by single particles aligned with the rotation axis.This result can be understood in terms of a super band built on aligned two-quasiparticle configurations which crosses the ground-state rotational band at a rotational frequency of $\text{h}\text{?}\text{ω ? 0.25}\text{MeV}\text{(I ? 28}\text{h}\text{?}\text{)}$. The E2 transition-matrix elements deduced from the experimental γ-yields agree within their errors with the rigid-rotor predictions up to the highest spins observed.The experimental results are discussed using the concept of rotation alignment and are compared with predictions of the rotation-vibration model and the interacting-boson model.     

Polaron self-energy in a dielectric slab

The lowering of the ground state energy of an electron below the bottom of the conduction band by virtue of its interaction with the longitudinal optical phonons is calculated as a function of the dielectric's thickness. The bulk result, —α$\text{h}\text{?}$;ω, is found as the thickness approaches infinity.     

Emission and laser-excitation spectra of the ≈A2Π ⇐ ≈X2Π transition of rotationally cooled bromochloroacetylene cation in the gas phase

Rotationally cooled bromochloroacetylene cations have been studied in the ≈X²Π_ω and ≈A²Π_ω (ω = $\text{3}\text{2}$, $\text{1}\text{2}$) states in the gas phase by two complementary spectroscopic techniques. The ≈A²Π ? ≈X²π band system was excited in emission by electron impact of a seeded supersonic helium free jet and as fluorescence by laser excitation of cations formed by Penning ionisation in a cooled environment. Comparison of the two sets of data locates the spin—orbit component bands and the origins of the systems, and allows the main spectral features to be vibronically assigned. The vibrational frequencies of most of the fundamentals are thus obtained to within ±2 cm^?1 for this cation in both the states.     

Electron-phonon coupling and phonon generation in normal-metal microbridges

The second derivative of current—voltage characteristic, $\text{d}{}^2\text{I}\text{d}\text{V}{}^2$, of a small orifice connecting two pieces of normal metals is shown to be proportional to the function $\text{G(ω) =}\text{α}\text{?}{}^2\text{(ω)F(ω)}$ at ω = eV, where F(ω) is the phonon density of states, and α&#x0303;² (ω) the square of the electron—phonon matrix element averaged over the Fermi surface and multiplied by the additional structure factor taking into account the geometry of the orifice. The constriction is shown to work, in a current-carrying state, as a source of non-equilibrium phonons emitted in the immediate vicinity of the orifice.     

Pure multi-photon ionization of the ground 1S and metastable 2S state of the hydrogen atom with plane-polarized light of threshold frequency

Formulas for N-photon ionization of the hydrogen atom states 1S and 2S with plane-polarized light at the threshold frequency $\text{ω=}\text{I}\text{N}\text{h}\text{?}$ (I ionization energy) are proposed and shown to reduce in the one-photon case to the well-known Stobbe expressions.     

Second backbending in the yrast line of 156Er

High spin yrast states of ¹⁵⁶Er were investigated using the reactions ¹⁴¹Pr(¹⁹F,4nγ) and ¹²³Sb(³⁷Cl, 4nγ), the latter in connection with a sum-crystal. In addition to the backbending at $\text{I = 12}\text{h}\text{?}$, a second one is found at $\text{I = 26}\text{h}\text{?}\text{;}$ and the yrast band is extended up to $\text{I = 32}\text{h}\text{?}\text{;}$. These results are interpreted in terms of a Hartree-Fock-Bogolyubov Cranking (HFBC) method. It is demonstrated that for deformations in the vicinity of the Strutinsky equilibrium deformation, both a 2qp proton band crossing the yrast band or a 4qp neutron band crossing the yrast band can cause strong secondary backbending.