Resonant Branch Research Articles

Fission decay of the giant quadrupole resonance forU234

The electrofission cross section for $^{234}\mathrm{U}$ from 5.5 to 25.4 MeV has been measured. From a combined analysis of it and the previously measured photofission cross section, using virtual-photon spectra calculated in the distorted-wave Born approximation, the $E2$ photofission cross section has been determined. Parameters of the fission-decay branch of the giant quadrupole resonance for this nucleus have been obtained. A comparison of the $E2$ and $E1$ integrated photofission cross sections for the even uranium isotopes shows that the $E1$ fission channel increases in strength more rapidly with fissility than does the $E2$ channel.NUCLEAR REACTIONS Measured $\ensuremath{\sigma}(e,f)$ for $^{234}\mathrm{U}$; deduced ${\ensuremath{\sigma}}^{E2}(\ensuremath{\gamma},f)$.

The role of deep shell nucleons in the formation of giant dipole resonance

The high energy branch of giant dipole resonance (GDR) is considered. The intensive excitation of this part of GDR is expected in certain (e, e′) reactions and muon capture. The large excitation probability is due to the axial component of the external field which leads to the intensive spin-flip transitions of deeply bound nucleons. The possible explanation of the local maximum observed in the spectra of neutrons following muon capture is given. The ways of experimental study of ths high energy resonance are pointed out. The consideration is carried out for32S,58Ni and88Sr nuclei. Due to the universality of GDR this choice covers rather broad region of nuclei.

Giant M2 and transversal E1 resonances in light nuclei

The cross section for inelastic backward electron scattering on 1p shell nuclei at incident energy E e = 70 MeV is calculated in the shell model. Comparison is made with radiative pion capture and muon capture. It is shown that the T > branch of the M2 resonance in (e, e') and the main maxima in the (π −, γ) response function are formed by identical partial transitions. We consider the basic features of the M2 resonance excitation in 1p shell nuclei and predict configurational and isospin splitting of this mode.

Investigation of 55Co Levels with the 54Fe (p, γ) 55Co Reaction I. Excitation and Decay Properties of Resonances

The nucleus 55Co has been studied through the reaction 54(p, γ)55Co. The yield curve has been measured in the proton energy range 0.80-2.37 MeV. The resonance bombarding energies and the corresponding 55Co excitation energies of 46 resonances are reported. The Q-value of the reaction has been determined to be 5064.2 ± 0.4 keV. The excitation energies of 34 levels below 5.6 MeV, fed by the resonance states, have been deduced. The gamma-decay of 29 resonances and of the 34 excited states below 5.6 MeV have been investigated, including 17 resonances and nine excited states for which the branching ratios are reported for the first time. Based on the new branching ratios, the revised resonance strength values of 2.6 ± 0.4 and 1.2 ± 0.2 eV are given for the Ep = 1722 and 1887 keV standard resonances, respectively. The relative strengths have been determined for 28 resonances. Using the present resonance strengths and branching ratios the transition probabilities of primary transitions from 14 resonance states have been calculated, including two observed analogue to analogue transitions.

The microscopic theory of pre-equilibrium decay and the photoproton spectra for medium nuclei

The paper deals with the photonucleon energy spectra for two branches of the giant resonance (T ) on the basis of the microscopic theory of the pre-equilibrium decay. The first stage of the reaction is described by the wave function obtained by matrix diagonalization based on particle-hole configurations (T ). The densities of the intermediate complex statesJ = = 1− (T ) are calculated with the Saxon-Woods potential. Specific calculations have been made for the nuclei of60Ni and90Zr.

Collective excitations of the polaron-gas

The dispersion of the collective excitations of a polaron-gas is calculated. It is found that the interaction between the L.O. phonons and the plasmons induces a relatively strong wave vector dependence in the ω +, ω - modes. This dispersion is primarily a consequence of the interaction of the L.O. phonons with the resonant plasmon branch in the pair excitation spectrum.

Magnetic Resonance Reviews

C P Poole Jr (ed) London: Gordon and Breach 1972 price £17.25 per volume (four issues) The editor's stated aim is to provide one publication which surveys the literature of all branches of magnetic resonance in such a manner that workers in this field can rely upon it for their prime source material. The intention is to survey the main branches annually, other areas less frequently.

Étude des niveaux du 32S formés au moyen de la réaction 28Si(α, γ)32S

Sixteen resonances were observed in the reaction 28Si(α, γ)32S in the range Eα= 4.2–6.0 MeV. Spins and parities have been determined by angular distribution and correlation measurements. The lifetime of the 4.29 MeV levels of 32S was deduced from a Doppler-shift attenuation measurement as τm = 94±30 fs. The transition strengths, deduced from measured resonance strengths and branching ratios, exhibit the expected inhibition of dipole transitions in self-conjugated nuclei.

Verification of Theory on Weak Turbulence Relating to the Sequence of Diffuse Plasma Resonances in Space

An interpretation of the sequence of diffuse plasma resonances observed by space probes (Alouette 2 and ISIS-1 satellites) is developed in terms of wave-particle nonlinear interaction in a weakly turbulent plasma including the electrostatic electron cyclotron harmonic wave instability. Observations and theory indicate that the center frequency fDn of the diffuse plasma resonance [nfH<fDn<(n+1)fH and fDn<fT] and the center frequency of the electrostatic wave resonance [nfH<fQn<(n+1)fH and fT<fQn] satisfy the condition of the wave-particle nonlinear interaction with the 2fH resonance according to the condition 2π[fH− ( fQn+2−fDn)]=[K(fQn+2)− k (fDn)]·v, where nfH, fT and v are the cyclotron harmonic frequency, the upper hybrid frequency, and the thermal velocity of the plasma, respectively; and k(f) is a wave vector as a function of a frequency f. The weaker diffuse plasma resonance branch observed at fDn1 (where fDn1>fDn) satisfies the condition 2π[fH− (fQn+1−fDn1)] = [k(fQn+1)−k(fDn)]·V. The longest time duration of the fDn resonance coincides with the most favorable condition for the electrostatic electron cyclotron harmonic wave instability which is obtained by solving the dispersion equation obtained for a linear approximation of the kinetic wave equation for the warm magnetoactive plasma. The electrostatic field due to the transmission of the intense rf pulse produces plasma turbulence involving nonlinear wave-wave interaction and temperature anisotropy which leads to the instability; this instability supplies energy to the turbulence. The fH and 2fH nonlinear wave-particle interactions in the turbulence heat the plasma to maintain the temperature anisotropy which lengthens the time over which the cyclotron harmonic wave instability conditions prevail; this process can be thought of as a feedback system. The results also indicate that the fH, 2fH and fQn waves are dependent on the fDn resonance generation.

Resonance strengths, branching ratios and mean lifetimes of nuclear energy levels in23Na

The gamma decay of the22Ne(p, y)23Na resonances in the proton energy rangeEp=1.0→2.0 MeV has been investigated with a 20cm3 Ge(Li) detector. Implanted targets were used. The absolute strengths of the strongest resonances were determined and the branching ratios of twenty resonance levels and several bound states are reported. Mean lifetimes of the levels atEx=2.078 MeV (18.7±3.5 fs), 2.393 MeV (580 −190 +370 fs), 2.641 MeV (88 −14 +20 fs), 2.985 MeV (4.0 −1.0 +1.3 fs), 3.679 MeV (24 −4 +5 fs), 3.915 MeV (7.4 −2.0 +2.5 fs) and 4.775 MeV (<2.0 fs) were obtained from measurements of the gamma ray Doppler shifts.

An experimental study of end effects for rectangular resonators on narrow channels

Quarter-wavelength resonators for harbour entrances and similar applications are usually designed and built without regard to the end effect. This paper describes tests on rectangular resonators using water waves of unique frequency in a long narrow wave channel fitted with a wave generator at one end, a wave absorber at the other end and suitable wave filters. In these tests the wavelength was kept constant while the geometry of the rectangular resonant branch canal was systematically varied. Wave transmission across the resonator, as well as wave reflexion upstream of the resonator was measured. The results clearly indicate a considerable effect of main channel width on optimum resonator width and resonator length, invalidating the usual resonance theory (which predicts complete reflexion of the incident wave train when the length of the branch canal is one-quarter of a wavelength). For example, it is found that, under certain conditions, quarter-wavelength resonators may not have any effect on the incident wave. The work described is limited to the first resonant mode and to semi-infinite domains on each side of the resonator.

Bounded, Resonantly Sustained High-Frequency Plasmas in a Magnetic Field and Densities High above Critical Density

It is shown that the wave properties of a magnetized plasma column, i.e., of a bounded magnetized plasma, at low incident high-frequency power determine the behavior of the column at high hf power. At high hf power, the energy absorbed is sufficient to sustain the plasma in one of its linear (i.e., low-power) resonant states. The plasma can either be sustained in one of its cold plasma resonant states or in its hot plasma resonant states. A partially quantitative theoretical picture can be drawn and maxima of the density as a function of B0 (static magnetic induction) exactly predicted. In this manner densities high above critical density (ωe &amp;gt; ω; ω is the angular frequency of hf field; ωe is the electron plasma frequency) can be obtained in the neighborhood of the lower cyclotron harmonics and along the upper branch of the cold plasma resonances. Ejection of plasma outside the interaction region between plasma and wave is observed. This ejection gives rise to plasma “tongues” with density maxima not correlated to the density of plasma in the interaction region. Low-frequency instabilities and the generation of harmonics are also investigated.

Production of K ∗(1300) and K ∗(1400) resonances in K +p interactions at 3.5 GeV/ c

In a recently completed experiment using 3.54 GeV/ c K + mesons in the BNL 80″ chamber, we have investigated the two prong + V o topology for resonance production. We have found evidence for the K ∗(1300) with a narrow width with K ππ decay modes and the K ∗(1400) with Kπ, K ∗π, Kϱ and Kω decay modes. We present resonance positions, widths, cross sections and branching ratios for these two K ∗ resonances.

High-Spin Baryons. V. Dynamical Model for Regge Recurrences of Inelastic Resonances: Numerical Results

Virtual transitions of the type $\ensuremath{\pi}{N}_{i}\ensuremath{\rightarrow}\ensuremath{\rho}{N}_{j}$, where ${N}_{i}$ and ${N}_{j}$ are arbitrary nucleon isobars, are considered as possible mechanisms for Regge recurrences. It is found that the largest one-pion-exchange forces coupling to ${(\ensuremath{\rho}{N}_{1})}_{L=0},{({\ensuremath{\rho}N}_{2})}_{L=0},\ensuremath{\cdots}$ [where ${N}_{1},{N}_{2},\ensuremath{\cdots}$ have spin-parity ${J}^{P} \mathrm{of} {S}^{P},{(S+2)}^{P},\ensuremath{\cdots}$] occur in the opposite-parity states ${(S+1)}^{\ensuremath{-}P},{(S+3)}^{\ensuremath{-}P},\ensuremath{\cdots}$. The most important couplings seem to be "diagonal," i.e., ${N}_{i}={N}_{j}$. In this case, isospin \textonehalf{} always dominates. If all $\ensuremath{\pi}{N}_{i}{N}_{i}$ couplings are of the same order of magnitude, then there are negative-parity trajectories that follow along with the positive-parity trajectories. It is found that the one-pion-exchange amplitudes lead to substantial violations of unitarity and to spectrum inversion for "off-diagonal" couplings (${N}_{i}\ensuremath{\ne}{N}_{j}$) involving large momentum transfers. To deal with this problem we introduce a one-parameter "form factor." Because of the uncertainties of coupling constants and form factor, predictions of resonance energies and branching ratios are somewhat adjustable. However, resonances occur in states having the correct quantum numbers, and the calculated widths are surprisingly good. Given the nucleon (${{N}_{i}}^{+}$) and ${{\ensuremath{\Delta}}_{i}}^{+}$ trajectories, we are led to the ${{N}_{i}}^{\ensuremath{-}}$ trajectory with $(T,{J}^{P})=(\frac{1}{2},{\frac{3}{2}}^{\ensuremath{-}}),(\frac{1}{2},{\frac{7}{2}}^{\ensuremath{-}}),\ensuremath{\cdots}$ and the ${{N}_{i}}^{\ensuremath{'}\ensuremath{-}}$ trajectory $(\frac{1}{2},{\frac{5}{2}}^{\ensuremath{-}}),(\frac{1}{2},{\frac{9}{2}}^{\ensuremath{-}}),\ensuremath{\cdots}$. In addition there is possibly another $(\frac{1}{2},{\frac{1}{2}}^{\ensuremath{-}}),(\frac{1}{2},{\frac{5}{2}}^{\ensuremath{-}}),\ensuremath{\cdots}$ sequence at rather high mass. The "exothermic" reactions for which $M({N}_{i})&gt;M({N}_{j})$ lead to possible isospin-$\frac{3}{2}$ resonances $(\frac{3}{2},{\frac{1}{2}}^{\ensuremath{-}}),(\frac{3}{2},{\frac{5}{2}}^{\ensuremath{-}}),\ensuremath{\cdots}$, but these calculations are not considered very reliable. The virtual-$f$ configurations $f{N}_{j}$ are also considered. These characteristically involve considerably larger momentum transfers than do the corresponding $\ensuremath{\rho}$-meson configurations. If the $f{N}_{j}$ amplitudes are modified by the same function used to repair the $\ensuremath{\rho}{N}_{j}$ couplings, no resonances result from the $f{N}_{j}$ mechanism. However, present methods of computing the magnitude of this high-momentum-transfer effect are unreliable. Extension of the vector-meson model to $\mathrm{SU}(3)$ leads to 8 and 1 trajectories with ${\frac{3}{2}}^{\ensuremath{-}},{\frac{7}{2}}^{\ensuremath{-}},\ensuremath{\cdots}$ and 8 alone for ${\frac{5}{2}}^{\ensuremath{-}},{\frac{9}{2}}^{\ensuremath{-}},\ensuremath{\cdots}$ and the doubtful companion ${\frac{1}{2}}^{\ensuremath{-}},{\frac{5}{2}}^{\ensuremath{-}},\ensuremath{\cdots}$. Generalization of the $f$ production mechanism to a tensor nonet ${T}_{9}$ leads to hitherto unobserved representations. ${P}_{8}\ensuremath{\rightarrow}{B}_{8}\ensuremath{\rightarrow}{T}_{9}+{B}_{8}$ would give 8, ${10}^{*}$, and 1 representations with spin ${J}^{P}$ of ${\frac{5}{2}}^{+},{\frac{9}{2}}^{+},\ensuremath{\cdots}$, and possibly ${\frac{7}{2}}^{\ensuremath{-}},{\frac{11}{2}}^{\ensuremath{-}},\ensuremath{\cdots}$, while ${P}_{8}+{B}_{10}\ensuremath{\rightarrow}{T}_{9}+{B}_{10}$ would give 10 and 27 representations with ${\frac{7}{2}}^{+},{\frac{11}{2}}^{+},\ensuremath{\cdots}$ if we have underestimated the importance of this effect. Hence present experimental evidence seems to support our conclusions about the relative importance of the vector- and tensor-meson production. The resulting baryon mass spectrum includes most of the prominent observed states. No wrong states are predicted. Some new resonances in the 2-BeV region are suggested.

Observation of resonance in the K O1K O1 system

We have analyzed 2560 events in the final-state K O 1K O 1n produced in π −p interactions at 5, 7 and 12 GeV/ c. We observe the S ∗ (1070), f O and A 2 decaying into K O 1K O 1. Resonance parameters, cross sections, and branching ratios are given.

Fermi Surface of Magnesium. I. Magnetoacoustic Attenuation

Geometric resonances in the ultrasonic attenuation have been studied in magnesium for sound propagated in the three principle crystallographic directions. A total of twenty different geometric resonance branches have been obtained. The assignment of these branches to Fermi-surface calipers shows that the magnesium Fermi surface is much more free-electron-like than currently thought. Three of the first four local pseudopotential Fourier expansion coefficients are estimated from data to be 5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ 1.0 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}2}$, and 1.7 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}2}$ Ry for the absolute value of the [$10\overline{1}0$], [0002], and [$10\overline{1}1$] coefficients, respectively. A two orthogonalized-plane-wave model is given for the lens-shaped piece of the Fermi surface in the third Brillouin zone, and various physical properties of this model are calculated and compared with experimental data.

Antiferromagnetic Resonance in CoF2, NiF2, and MnCO3

The far-infrared transmission spectra of CoF2, NiF2, and MnCO3 have been measured from 3 to 100 cm−1 using the techniques of Fourier-transform interferometry. Antiferromagnetic resonance branches have been found in CoF2 at 28.5 cm−1 and 36 cm−1 at temperature T≈0, each of which splits in a magnetic field along the c axis. These resonances have been studied as a function of field, temperature, and uniaxial stress. Antiferromagnetic resonance at 31.1 cm−1 and ferromagnetic resonance at 3.33 cm−1 in NiF2 at T≈0 have been studied as a function of field and temperature, and the results are compared with Moriya's theory. Antiferromagnetic resonance has been observed at 4.13 cm−1 in MnCO3 at T≈0.

THE INFLUENCE OF RARE EARTH IONS ON FERRIMAGNETIC RESONANCE

本文利用关联函数的方法(久保理论),讨论了强交换耦合系统的亚铁磁共振,给出了系统总磁化率张量的一般表达式,由此可以定出铁磁支与交换支的共振场H0(或共振频率)和峯宽2△ω。所得结果表明,所谓快弛豫及慢弛豫机理不过是铁磁共振的两个分支(横分支与纵分支)。横分支相应于J及S的横向磁矩之间的耦合运动J,S分别为希土离子及铁离子的磁矩),而纵分支相应于J的纵向分量与S的横向分量之间的耦合运动。由于晶场及各向异性交换场的作用,J的量子化方向与S的量子化方向偏离一个角度φ。此外由于交换作用的各向异性,在交换作用哈密顿J·λ·S中,张量λ的非对角元可以相当大。结果表明,纵分支对峯宽的贡献近似地正比于φ2及λi3(i=1,2)。根据2△ω的一般表达式,在极低温下(4.2°K以下),峯宽主要是由横分支决定的。沿某些晶轴方向?a,当希土离子最低两个能级接近“交叉”时,共振场及峯宽应该出现反常峯值,这在实验上已经得到了证实。当温度升高时,纵分支将逐渐“压过”横分支。当纵向弛豫频率达到高频场的频率ω时,峯宽将出现极大值,一般实验中观察到的就是这个极大值。当温度继续升高时,横分支又将起主要作用。当横向弛豫频率接近相应于希土离子最低两个能级之间的间距ω21时(?=1),峯宽将出现第二个极大值。实验上只有沿希土离子最低两个能级接近交叉的方向进行测量时,才有可能观测到第二个峯值。当频率足够高,满足|ω21(?a)-ω|<<ω的条件时,在极低温下,将出现由横分支决定的尖锐的峯宽极大值。根据所得理论结果,除上述现象外,还可以统一地解释在希土石榴石铁氧体中观测到的下列实验事实:有效旋磁比随温度的显著变化;在抵消点附近峯宽的急剧上升;在镱铁氧体中观测到的在峯宽极大值出现的温度共振场显著上升等。指出了经典磁矩运动方程的局限性,在铁氧体中,晶场的作用与交换场其大小可以相比时,利用经典方程求解所得出的结果只能定性地解释某些与希土离子具体能级结构无关的现象。

The 23Na(p, γ) 24Mg reaction (II)

Gamma-ray angular distributions and γ-γ angular correlations have been measured at six 23Na(p, γ) 24Mg resonances in the E p = 300–800 keV region. Analysis of these data with an electronic computer yields spin and parity assignments: J π = 2 (+), 1 (+), 2 −, 3 (+) and 2 + to the resonances at E p = 308, 511, 591, 676, 738 and 743 keV, respectively. The even parities in brackets are regarded very probable. In each of these cases odd parity would imply the existence of an M2 transition with a strength of at least 0.5 Weisskopf units. The same measurements give J π = 2 + for the 24Mg level at E x = 7.35 MeV. Single spectra and γ-γ coincidence spectra measured at the weak E p = 251 and 374 keV resonances yield the resonance branching ratios.

A natural explanation of the narrow pion-pion resonance

Resonant branches of pi - pi solutions obtained using the delta approximation valid at small values of the interaction constant lambda are extended into the domain in which lambda is not small, using electronic- computer calculations. F eatures and physical content of the solutions are discussed. (L.N.N.)