Four-parameter coincidence study of the 6Li(6Li, α)2α reaction

Quasifree mechanism in theLi6+Li6→3αreaction at low energy

“…The 6 Li + 6 Li → 3α experiment was performed using the EN Tandem Van de Graaff accelerator of the Ruđer Bošković Institute in Zagreb. A 3.1-and 2.5-MeV 6 Li ++ Tandem beam with intensity of about 3 nA, was delivered onto an isotopically enriched 6 LiF target, 87-μg/cm 2 thick, evaporated on a carbon backing, 27-μg/cm 2 thick.…”

“…In previous years, the 6 Li + 6 Li → 3α reaction around the Coulomb barrier was experimentally investigated by several authors [1][2][3][4][5][6][7][8][9][10][11][12][13][14], in several cases for astrophysical studies via the Trojan Horse method [15][16][17][18][19][20][21][22]. Both sequential decay (SD) through 8 Be excited states and direct processes were seen to contribute to the reaction cross section.…”

“…Both sequential decay (SD) through 8 Be excited states and direct processes were seen to contribute to the reaction cross section. Such direct contributions have been mainly interpreted as from quasifree (QF) processes, in which an α cluster, either in the target or in the projectile, is spectator of the 6 Li+d → 2α virtual reaction. The two QF processes, referred to as quasifree reactions in the target (QFR) t and in the projectile (QFR) p show cross-section enhancements in the α-α energy and angular correlations.…”

“…They also found that at 2 MeV of beam energy events did not fall in the two kinematical regions corresponding to QF processes, but rather in an intermediate one providing a huge peak in the α-α angular correlation spectra. This effect was interpreted [10,11] as due to the long-range Coulomb interaction which slows down the relative motion of the two 6 Li nuclei. The two 6 Li would interact only after they are stopped by the Coulomb repulsion and the two standard QF processes are no longer distinguishable.…”

“…These tentative structures may belong to the two QF processes. This has triggered a new higher resolution experimental work on the 6 Li + 6 Li → 3α reaction thanks to the advances in the detection systems and electronic devices available today and to the more sophisticated event-by-event data analysis available nowadays. The present paper reports a new measurement performed at 3.1 and 2.5 MeV of beam energy.…”