Exotic Reaction Research Articles

Evidence of a Direct Process in the (He4,He8) Reaction

The transfer mechanism for the exotic ($^{4}\mathrm{He}$, $^{8}\mathrm{He}$) reaction has been investigated by measuring the angular distribution for the reaction $^{64}\mathrm{Ni}$($^{4}\mathrm{He}$, $^{8}\mathrm{He}$)$^{60}\mathrm{Ni}$. The structure in the angular distribution is reproduced by a direct four-neutron-cluster transfer. In addition, the relative ($^{4}\mathrm{He}$, $^{8}\mathrm{He}$) cross sections from $^{64}\mathrm{Ni}$ and $^{58}\mathrm{Ni}$ are predicted correctly if collective effects are included in the spectroscopic factors.

Charge Exchange Reactions in the Peripheral Orbit Model

In our previous papers we have proposed the peripheral orbit model by introducing a peripheral Regge trajectory in the direct channel. The radius and absorptivity of the orbit are related to Rea and Im a, respectively. The width of the orbit is introduced through the factor e(J, s) (O[exp(-2\IIJ/p)] as ReJ-->oo) and Ima. In this article the model is applied to exotic reactions into which no peripheral Regge trajectory can be introduced. The exotic forward reaction amplitudes are defined from their u-channel reaction amplitudes through analytic continuation. The imaginary parts of the exotic reaction amplitudes are shown to have non-peripheral components due to the analytic continuation of the factor e(J, s). The model is applied to n-p-tn°n, n-p->r;n, K+n--'>K0p and K-p--'>K 0 n. § l. Introduction In this article we discuss non-cliffractive two-body reactions. As is well known, the interaction between haclrons is strongly absorptive especially when the impact parameter of the collision is small. In spite of the strong absorption near the center, the interaction in the peripheral region is considerably transparent and an incoming hadron is assumed to revolve in a peripheral orbit around a target hadron if the interaction is attractive there. 1l' 'l In our pre,·ious papersn we have considered the reactions the u-channels of which are ec;:otic, i.e., x-p ;K_on and pj.J-->K-x-. The amplitudes of these re· actions receive contributions only from the resonances in the s-channel in the two­ component theory. 3l In this article we consider the reactions the u-channels of which are non-exotic, such as ;-:-jJ->7':071, ;-:-P->'ljn and J( n- > K 0j.J. The real parts of the amplitudes of these reactions receive contributions from the resonances in the u-channels. The model will be introduced in § 2 and will be applied to forward rr-j.J--+7r 0n, ;-:-p--+!Jn, x-n->K0p and x-p->K0n reactions at high energies (I tl <l.S(GeV)' and

Polarization calculations in a box-diagram model

A box-diagram model is presented in which it is assumed that the exotic exchange reaction $pi$⁻p $Yields$ $Sigma$⁻K⁺ occurs as a result of multiple nonexotic exchanges, e.g., $pi$⁻p $Yields$ rho$sup 0$n $Yields$ $Sigma$⁻K⁺, and each step of this process is evaluated under t- channel single-pole approximations. The imaginary part thus obtained when multiplied by the real contributions of one-particle-exchange diagrams accounts for the main features of the polarization data of $Sigma$⁻. (AIP)

Limits of Applicability of the Firefly Luminescence ATP Assay for the Detection of Bacteria in Clinical Specimens

ATP measurement can be used as an indicator of biological mass, and the extreme sensitivity of the firefly ATP assay has led to its use in bacterial detection systems. Clinical specimens present problems not encountered with cultured isolates of known bacterial species. The lower limit of sensitivity for detecting bacteria using the firefly assay is 100,000 bacteria per ml. Non-bacterial ATP, which is probably present in all clinical specimens, produces false-positive results unless it is completely destroyed, and this destruction must be carried out under conditions that do not affect bacterial ATP. A cause of false-negative results is the presence in all urine specimens of unidentified materials that inhibit the luminescent enzymic reaction. These considerations indicate that application of the firefly ATP assay in bacterial detection systems for clinical specimens is feasible only if a preparatory step separates bacteria from interfering materials and from non-bacterial sources of ATP, and concentrates microorganisms to measurable levels. These limitations sharply curtain the applicability in diagnostic microbiology of this exotic chemical reaction.

Impact of Lasers in Spectroscopy

The theme to be explored in this meeting is that the laser is far more than just another light source for spectroscopists; it will be amply demonstrated that the laser has been the basis of a qualitative revolution in this branch of science, just as the development of NMR has profoundly altered the practice of organic chemistry, or as the digital computer has made modern systems analysis possible. In this paper we will consider some of the unique features of the laser that have made this revolution possible, and some of the applications of these features. The most striking aspect of the laser is the enormous quantity of optical power and/or energy that is capable of being generated. This feature combines with the spectral purity and beam collimation which are consequences of the coherence of the laser output to produce a spectral surface brightness which may be 16 or more orders of magnitude greater than for conventional light sources. The phase coherence of the laser output is another unique feature, and improvement in time resolution over conventional sources by five or more orders of magnitude can also be obtained. These features have already been exploited in a number of ways. Selective excitation of molecular energy levels has opened new possibilities in fluorescence spectroscopy, not only in the visible, but also in the hitherto inaccessible infrared region. New double-resonance techniques have been developed, and Raman spectroscopy has experienced a renaissance. Selective excitation is now likely to become very important in chemical processing as well. Saturated-absorption techniques have made possible Lamb-Dip spectroscopy and the development of optical frequency standards. Measurements can now be made on molecular beams, providing information about exotic reaction conditions and the details of scattering events. The use of coherent light sources opens the possibility of a wide variety of optical analogues of magnetic-resonance phenomena, such as pulse and echo effects, coherent transient decays, etc. A

Odorico zeros for exotic exchange processes

On assuming that the exotic exchange reaction pi -p to Sigma -K+ occurs as a result of multiple non-exotic exchanges pi -p to rho 0n to Sigma -K+, the author finds that the imaginary parts of the invariant amplitudes A and B for the above reaction show Odorico zeros at almost fixed and small value of momentum transfer. The recent phase shift analysis of Langbein and Wagner supports his result.