A study of 3He capture in light nuclei

Excitation functions at θ = 90° have been measured for ${}^{16}\text{O}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0?2,\; 3?5,\; 6}}\text{)}{}^{19}\text{Ne}$, ${}^{15}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1?4}}\text{)}{}^{18}\text{F}\text{,}{}^{14}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1,2,3}}\text{)}{}^{17}\text{F}$, and ${}^{20}\text{Ne}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^{23}\text{Mg}$, in the range E_{3He = 3–19 MeV}. The first reaction has also been studied at θ = 40°. Excitation functions at 90° have also been measured for and ${}^4\text{He}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^7\text{Be}$ for E_3He = 19–26 MeV. Angular distributions have been measured for the first four reactions.For the most excitation functions, a broad peak is observed, several MeV wide, centred at about E_x≈ 20 MeV. Superimposed on this, in some cases, are narrower peaks, with width ≈ 1 MeV. Energies and widths have been extracted for all resonances.Cluster-model calculations have been carried out, using methods similar to those which have proved successful for low-lying states in A= 18–19 nuclei. No satisfactory correspondence with the present results was found. The shell model has been used to calculate Γ_3He and Γ_γ for 1?ω excitations in the final nuclei. These generally show good agreement with the trends of the experimental data. The results are consistent with the excitation of the giant dipole resonance in ³He capture, but much more weakly than in proton capture.     

Study of the reactions 118Sn(d,t) and98Mo(d,t): (I). Spectroscopy of 117Sn and 97Mo

The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.0 MeV for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to six states of ¹¹⁷Sn (E_x = 0.0, 0.16, 0.31, 0.71, 1.02 and 1.18 MeV), for ${}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to eight states of ⁹⁷Mo (E_x = 0.0, 0.68, 0.72, 0.89, 1.12, 1.28, 2.39 and 2.52 MeV), and for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{d}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{d}\text{)}$. Deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the $\text{(}\text{d}\text{,}\text{t}\text{)}$ results. Comparison of the measurements and DWBA predictions for σ(θ) and for iT₁₁(θ) allows unambiguous determination of tl_n and j_n for all ¹¹⁸Sn(d, t) and most ⁹⁸Mo(d, t) transitions. Differences in the triton energy relative to the Coulomb barrier cause marked qualitative differences in the measured cross sections and analyzing powers between ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions of the same l_n and j_n.     

Angular correlation experiments in the reactions 2H(α, nα)p and 2H(α, pα)n and comparison with the Faddeev theory and the resonating group method

At the Hamburg Isochronous Cyclotron angular correlation experiments were carried out in the reactions ²H(α, nα)p and ²H(α, pα)n, in order to determine the tensor polarization of the ground-state resonances ${}^5\text{Li}\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$ and ${}^5\text{He}\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$, respectively. We find that the observables for the two mirror reactions ${}^2\text{H}\text{(α,}\text{n}\text{)}{}^5\text{Li}\text{and}{}^2\text{H}\text{(α,}\text{p}\text{)}{}^5\text{He}$ are charge-dependent. This result is interpreted as evidence for a violation of charge symmetry.In the whole phase-space region absolute break-up cross sections are generally well reproduced by the Faddeev theory. On the other hand, we find that the resonating group method which has up to now been mainly applied to two-body reactions can also provide valuable information for break-up reactions. The predictions of Hackenbroich, Schütte and coworkers are in quite good agreement with the measured tensor polarization of ⁵He and ⁵Li and the corresponding angular correlation functions.     

(3He, 2n) excitation functions for some light nuclei

Excitation functions have been measured for the reaction ⁹Be(³He, 2n)¹⁰C over the range $\text{E(}{}^3\text{He}\text{) = 10–41}\text{MeV}$ and for the reaction ²⁷Al(³He, 2n)²⁸P over the range $\text{E(}{}^3\text{He}\text{) = 14–41}$ MeV by detecting β-delayed γ-rays. An excitation function has also been measured for the reaction ²⁴Mg(³He, 2n)²⁵Si over the range $\text{E(}{}^3\text{He}\text{) = 21–43}\text{MeV}$ by detecting β-delayed protons.     

Analyzing power in the continuum of the (p, αx) and (p, τx) reactions on 12C, 27Al, 58Ni, 90Zr, 209Bi at Ep = 72 MeV

We have measured cross sections and analyzing powers in the continuum of the ($\text{p}$, αx) and ($\text{p}\text{, τx}$) reactions for ¹²C, ²⁷Al, ⁵⁸Ni, ⁹⁰Zr and ²⁰⁹Bi target nuclei, using 72 MeV polarized protons. The systematics we have found in the behaviour of the differential cross section and of the analyzing power of the ($\text{p}\text{, αx)}$ reaction is discussed and similarities in the shape of the ⁴He and ³He angular distributions are pointed out. For the ${}^{27}\text{Al}\text{(}\text{p}\text{, α}\text{x}\text{)}\text{and the}{}^{90}\text{Zr}\text{(}\text{p}\text{, αx)}$ reactions as well as for the ${}^{58}\text{Ni}\text{(}\text{p}\text{, τ}\text{x}\text{)}$ reaction, a comparison with theoretical predictions of recently developed direct-reaction models is presented. It is shown that the MSDR model can describe successfully the cross section and the analyzing power of the $\text{(}\text{p}\text{, α}\text{x}\text{)}$ reaction in the continuum. The influence of quasi-free processes in the $\text{(}\text{p}\text{, α}\text{x}\text{)}$ reaction is demonstrated. We have found a surprisingly large analyzing power of the $\text{(}\text{p}\text{, α}\text{x}\text{)}$ reaction at backward angles, especially for heavy nuclei, contrary to expectations from conventional preequilibrium models.     

Theory of the decay process of metastable state

The short-time and long-time behavior of the distribution function P(x, t) are investigated in the laser model by using the generating function $\text{G(α,}\text{β}\text{;t) = σ(α-y(t)) Π}{}^{\mathrm{\infty }}{}_{\mathrm{n=2}}\text{σ(β}{}_{\mathrm{n}}\text{- M}{}_{\mathrm{n}}\text{(t)),}\text{where}\text{y(t)  ?xP(x, t)}\text{d}\text{x}\text{and}\text{M}{}_{\mathrm{n}}\text{(t)  ?(x - y(t))}{}^{\mathrm{n}}\text{P(x,t)}\text{d}\text{x}$.     

Investigation of level energies and B(E2) values for rotation-aligned bands in Hg isotopes

High spin states in ^{191, 192, 193, 195, 197, 199}Hg were investigated by observing γ-rays and conversion electrons in the compound reactions ${}^{\mathrm{192,\; 194,\; 198}}\text{Pt(α, x}\text{n}\text{)}\text{and}{}^{192}\text{Pt}\text{(}{}^3\text{He}\text{, 4}\text{n}\text{)}$. In ¹⁹⁷Hg the decoupled band built on the $\text{13}\text{2}{}^{\mathrm{+}}$ state and the semi-decoupled negative-parity band are observed up to $\text{I}{}^{\mathrm{\pi }}\text{=}\text{41}\text{2}{}^{\mathrm{+}}\text{and}\text{33}\text{2}{}^{\mathrm{?}}$, respectively. A careful investigation of ¹⁹⁹Hg revealed no new high spin states above the previously known levels with $\text{I}{}^{\mathrm{\pi }}\text{=}\text{25}\text{2}{}^{\mathrm{+}}\text{and}\text{31}\text{2}$^?. Half-lives were determined for the 10⁺, 7^?, 8^? and 16^? states in ¹⁹²Hg, the if$\text{33}\text{2}{}^{\mathrm{+}}$$\text{states in}{}^{\mathrm{191,193}}\text{Hg and the}$ (frc states in ^{191, 193, 195, 197}Hg. The systematics of the level energies and B(E2) values for the positive-parity ground and $\text{13}\text{2}{}^{\mathrm{+}}$ bands and the negative-parity semi-decoupled bands in ^190–200Hg is discussed.     

Infra-red asymptotic behaviour of the one-fermion green's function in a scalar model with isospin

In a theory where massive fermions interact with a massless scalar field of isospin 1, the behaviour of the one-fermion Green's function is found to differ from the free Green's function by a factor $\text{(1 ? (2g}{}^2\text{/π}{}^2\text{)1}\text{n}\text{m|x ? y|)}{}^{\mathrm{<mtext>?</mtext><mtext>3</mtext><mtext>8</mtext>}}$, in the limit of large separation |x ? y|.     

Devil's attractors and chaos of a driven impact oscillator

The motion of a driven elastic impact oscillator: $\text{x}\text{?}\text{+ 0.4}\text{x}\text{?}\text{+ x =}\text{cos}\text{(ωt)}$, x > 0 and $\text{x}\text{?}\text{(t}{}^{\mathrm{+}}\text{) = -}\text{x}\text{?}\text{(t}{}^{\mathrm{?}}\text{)}$ at x = 0, is studied for ω ≈ 2?4. The oscillator exhibits Feigenbaum's bifurcations (computed δ ≈ 4.70), the Feigenbaum and intermittent transitions to chaos, crises in chaos and a strong hysteresis region for ω ≈ 3.18–3.20 where the impact/period ratios of a group of attractors show the Devil's staircase behaviour with locking values between $\text{3}\text{5}$ and $\text{3}\text{4}$.     

Laser excitation spectra of He2

Metastable $\text{a(2sσ)}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ He₂ molecules are produced by a dc discharge in a flowing He stream. Laser excitation downstream of the discharge produces excitation spectra for a number of He₂ states. LIF spectra are observed for the $\text{(npπ)}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ series for n = 4–9, excepting 5 and the $\text{(npπ)}{}^3\text{Π}{}_{\mathrm{g}}$ series for n = 5–15.     

Coherent pion production in 3He3He collisions

A model is proposed to describe the near-threshold production of pions in the ${}^3\text{He}\text{(}{}^3\text{He}\text{, π}{}^{\mathrm{+}}\text{)}{}^6\text{Li}$ reaction. Taking experimental data on the ${}^3\text{He}\text{(p, π}{}^{\mathrm{+}}\text{)}{}^4$He process as input the cross sections for the first three levels of ⁶Li are reproduced semi-quantitatively.     

Pion absorption effects in the reaction 3H(π+, π0)3He

We show that in Glauger theory the angle integrated cross section for ${}^3\text{H}\text{(π}{}^{\mathrm{+}}\text{, π}{}^0\text{)}{}^3\text{He}$ has no peak as a function of energy through the 3,3 resonance region, thus suggesting a direct measurement to elucidate the nature of (π⁺, π⁰) reactions.     

Decay pathways and entry-state population in (α, xnγ) and (3He, xnγ) reactions on 150Nd

Exclusive neutron spectra and angular distributions have been measured by n-γ coincidence techniques for $\text{(α, x}\text{n}\text{γ)}\text{and}\text{(}{}^3\text{He}\text{, x}\text{n}\text{γ)}$ reactions on ¹⁵⁰Nd in the 25–44 MeV range. The results show that pre-equilibrium processes dominate low-energy light-ion induced reactions at certain beam energies. Analysis of the yrast γ-ray cascades in the residual nuclei shows that a well-defined minimum entry-state spin exists in final nuclei populated by pre-equilibrium processes. This in turn implies the existence of a minimum classical impact parameter for these reactions. These results are discussed in terms of phenomenological models of the reaction mechanisms.     

The uniform and the strong topology on realizations of the algebra of polynomials

It is shown that under quite general assumptions on the operators A₁,…,A_n (unbounded, symmetric) and on the domain $\text{D}$ on the realization $\text{P}\text{(A}{}_1\text{,…,A}{}_{\mathrm{n}}\text{)}$ of the algebra of polynomials $\text{P}\text{(x}{}_1\text{,…,x}{}_{\mathrm{n}}\text{)}$, the strongest locally convex topology τ_st coincides with the uniform topology τ_$\text{D}$ as well as with the strong operator topology τ_s. In the case n = 2 some conditions are given, under which these general assumptions are fulfilled.     

Self-adjointness of the minimal Schrödinger operator with potential belonging to L1, loc

Let $\text{0 ?q(x) ∈L}{}_{\mathrm{1,loc}}\text{(}\text{R}{}^{\mathrm{m}}\text{)}$,m? 1.Consider the operatorT₀ = ?Δ+q with domain consisting of all bounded measurable functions $\text{u(x), x ∈}\text{R}{}^{\mathrm{m}}$, having bounded support, for which the distribution ?Δu+qu belongs to $\text{L}{}_2\text{(}\text{R}{}^{\mathrm{m}}\text{)}$. The main result of the paper is essential self-adjointness of $\text{T}{}_0\text{in L}{}_2\text{(}\text{R}{}^{\mathrm{m}}\text{)}$. The proof is independent of a method due to Kato who recently established the self-adjointness of a maximal Schrödinger operator corresponding to such potential.     

Anomalous gamma-ray multiplicity distributions-evidence for pre-equilibrium neutron emission

Multiplicity distributions and 〈E_γ〉 have been measured for the ${}^{124}\text{Sn}\text{(}{}^{40}\text{Ar}\text{, x}\text{n}\text{)}{}^{\mathrm{164?x}}\text{Er}$ reaction at E(Ar) = 161, 182, 189, 209, and 236 MeV. The data at E(Ar) = 236 MeV indicate that pre-equilibrium neutrons are emitted. These data, together with other reactions leading to Er final systems, are discussed in terms of pre-equilibrium mechanisms.     

Hyperfine structure of CH3OH

Hyperfine structure of the (0, 0, 1) - (1, 0, 1) transition of methanol has been investigated by beam absorption and of the (J, 1, 3?) → (J, 1, 3+) transitions for J = 2, 3, and 6 by beam-maser spectroscopy. The best-fit results for the spin-rotation and spin-spin coupling constants $\text{C}{}_{\mathrm{JK\tau \pm }}{}^{\mathrm{(i)}}$ and $\text{D}{}_{\mathrm{JK\tau \pm }}{}^{\mathrm{(i)}}$, respectively, are in kHz¹: $\text{C}{}_{101}{}^{\mathrm{(1)}}\text{= 2.4(10)}$, $\text{C}{}_{101}{}^{\mathrm{(2)}}\text{= ?0.6(10)}$, $\text{D}{}_{101}{}^{\mathrm{(1)}}\text{= ?13.8(9)}$, $\text{D}{}_{101}{}^{\mathrm{(2)}}\text{= 7.0(9)}$, $\text{C}{}_{\mathrm{213?}}{}^{\mathrm{(1)}}\text{= ?5.0(10)}$, $\text{C}{}_{\mathrm{213?}}{}^{\mathrm{(2)}}\text{= ?5.5(10)}$ and ($\text{C}{}_{\mathrm{J13?}}{}^{\mathrm{(2)}}\text{- C}{}_{\mathrm{J13+}}{}^{\mathrm{(2)}}\text{) = 0.98(9)}$.     

Determination of the isotopic shift of the first resonance line in Cs(I) spectrum for the isotopes 131Cs, 132Cs,and 136Cs

The isotope shifts of the resonance line $\text{λ = 8521}\text{A}\text{?}$ of ¹³¹Cs, ¹³²Cs, and ¹³⁶Cs with respect to ¹³³Cs were determined by a new scanning technique to be $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{131}\text{Cs}\text{) = +1.70(40)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{132}\text{Cs}\text{) = ?0.95(80)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{136}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{) = ?4.0(3.0)}\text{mK}$. In accordance with results from other Cs isotopes and neighbouring elements they show the change 〈δr²〉 in the second radial moment of the nuclear charge distribution to be a factor of 5 to 10 smaller than expected from the model of uniform charge distribution. Integral isotope shifts over the isotopic chains of Xe, Cs, and Ba were analyzed in terms of collective models. Assuming an isotopic shift discrepancy of 0.5 for the nuclear volume shift it was possible to derive deformation parameters $\text{〈β}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in quantitative agreement with those from B(E2) measurements.