DOI 10.1140/epja/i2001-10221-1 Eur. Phys. J. A 15, 389–397 (2002) T HE EUROPEAN P HYSICAL JOURNAL A 16 O-induced transfer reactions on 90 Zr V. Jha 1 , B.J. Roy 1,2, a , A. Chatterjee 1 , H.S. Patel 1 , B. Srinivasan 1 , M.G. Betigeri 1 , and H. Machner 2 1 Nuclear Physics Division, B. A. R. C., Mumbai-400085, India 2 Institut f¨ ur Kernphysik, Forschungszentrum J¨ ulich, Germany Received: 16 November 2001 / Revised version: 31 January 2002 / Published online: 19 November 2002 – c  Societ` a Italiana di Fisica / Springer-Verlag 2002 Communicated by D. Guerreau Abstract. Cross-section for transfer reactions 90 Zr( 16 O, X) have been measured at an incident energy of 90 MeV. The angular distribution of the elastic scattering 90 Zr( 16 O, 16 O) 90 Zr, the inelastic scattering to excited states of 90 Zr, the one-nucleon transfer reactions 90 Zr( 16 O, 15 N) 91 Nb (g.s., 0.104 and 3.37 MeV states), 90 Zr( 16 O, 15 O) 91 Zr (g.s. and 2.17 MeV state) 90 Zr( 16 O, 17 O) 91 Zr (g.s.) and the two-nucleon transfer reactions 90 Zr( 16 O, 14 C) 92 Mo (ground and 1st excited states) are analyzed in the coupled-reaction-channel (CRC) formalism. Starting with a double-folded real potential, the elastic-scattering angular distribution is calculated using the CRC code FRESCO. The absorptive potential is then generated through the coupling of various inelastic and transfer processes that occur at the nuclear surface. Addition of a short-range imaginary potential in the coupling scheme, whose purpose was to take into account the effect due to loss of flux in fusion channel, reproduces the measured elastic-scattering angular distribution. A good description of all the quasi-elastic data has been achieved and the absolute magnitudes are reproduced without any arbitrary normalization. The relative importance of the one-step cluster transfer of two protons vs. the two-step successive transfer has been studied. PACS. 25.70.Hi Transfer reactions – 25.70.Bc Elastic and quasielastic scattering 1 Introduction Nucleon(s) transfer between heavy ions represents an im- portant reaction mechanism to understand 1) spectro- scopic aspects and correlation effects in nuclei, 2) the tran- sition from the quasi-elastic to the deep-inelastic regime and 3) coupling effects with other competing channels [1– 3]. Transfer reactions are also a competitive tool for the production of neutron-rich nuclei and give access, with the availability of radioactive beams, to a wide field of nuclear structure studies in the far off-stability region. In view of its importance, a large amount of work has been carried out and is reported in the literature on heavy-ion trans- fer reactions. One of the main emphasis of all these works was to understand the reaction mechanism. The mecha- nism in which a large number of nucleons are transferred from projectile to target or viceversa is not well under- stood. The presence of a multi-step transfer involving se- quential transfer, inelastic excitations prior or after the transfer etc., in addition to the usually dominant direct cluster transfer complicate the reaction mechanism. The number of such possibilities increases dramatically with the number of transferred nucleons and consequently it becomes more and more difficult to estabilish the reaction a e-mail: b.roy@fz-juelich.de mechanism. On the experimental side, unambiguous data on multi-nucleon transfer reactions is not easily available. A good charge, mass and energy resolution and at the same time a high detection efficiency is a difficult task to achieve, especially, when both the colliding nuclei are heavy. In a series of measurements carried out by us at the 14UD pelletron accelerator facility at Mumbai, In- dia, reactions corresponding to up to twelve-nucleon trans- fer have been observed. In these experiments a variety of target ( 56 Fe, 88 Sr, 90 Zr, 115 In) and projectile ( 12 C, 16 O, 18 O) combinations was used. A good charge and mass sepa- ration up to Z = 8, A = 18 has been achieved using ΔE-E surface barrier detector telescopes. The work on 12 C+ 88 Sr, 12 C+ 115 In and 12 C+ 56 Fe has already been reported in our earlier communications [4–8]. The empha- sis was on the understanding of the reaction mechanism aspects, in particular, the importance of one-step direct vs. multi-step sequential transfer and channel coupling ef- fects amongst elastic, inelastic and transfer reactions. In the present work, we report an analysis of various quasi-elastic processes induced in the collision of 16 O ions with 90 Zr nuclei at an incident energy of 90 MeV. The coupled-reaction-channel(CRC) formalism [9] allows one to couple all possible direct/indirect channels in a heavy- ion–induced reaction and hence the effect of channel cou-