1. 1 S. A. Karamian I. Elementary microscopic states of complex nuclei are manifested: in radioactive decay processes; in specific nuclear reactions as: a) Scattering; b) Coulomb excitation; c) Stripping reactions. TO THE MECHANISM OF PARTICLE RELEASE IN NUCLEAR REACTIONS Joint Institute for Nuclear Research, Dubna, Moscow region, Russian Federation

2. 2 II. Bulk reactions proceed via continuum of excited levels being treated within statistical and macroscopic approaches. Among them could be listed the most abundant processes as: Compound nucleus formation and decay; Fission; Nucleon emission from highly excited nuclei, and so on. III. In statistical model, the nucleus is characterized by temperature, entropy and total angular momentum. All nucleons are assumed identical and their individual quantum numbers make no significance. IV. It would be yet interesting to deduce the status of nucleons inside a nuclear volume from the data reached in reaction experiments. V. Some examples of intrinsic structure manifestation are given below.

3. 3 I.Observation of low probability for ( , α) reactions that requires the pre-formation factor. Conclusion: α-clusters and multi-quark objects may be present in nucleus but with low probability ~10–2; II.In reactions with heavy ions, the probability of α emission is oppositely very high. Conclusion: alphas are formed through the special mechanism of internal coalescence; III.Observation of an excess in the T l values for emission of neutrons with l ≥3 at INNA experiment. Internal single nucleon orbits possess a high momentum, but centrifugal barrier suppresses their emission. The re- arrangement of orbits is needed. The enhanced yield of INNA means an effect of internal states; MANIFESTATION OF INTERNAL STATES IN REACTIONS OF STATISTICAL MECHANISM

4. 4 IV.Observation of the preferential population of high-spin states in ( , n) and ( , p) reactions with isomeric targets. Survival of the structure selectivity indicates incomplete mixing of specific states even despite excitation energy of E* ≈ 7-15 MeV; V. The re-arrangement of internal states in advance of particle emission suppresses the absolute reaction rate as compared to the standard statistical estimates. VI.Some major details are given below.

5. 5 REFERENCES TO THE ORIGINAL WORKS I. Reactions induced by 23 MeV bremsstrahlung Ref. [1]: S.A. Karamian, “Threshold and spin factors in the yield of bremsstrahlung-induced reactions”. Preprint JINR, E15-2012-65, Dubna, to be published in Phys. of Atomic Nuclei. Ref. [2]: S.A. Karamian, “Yield of bremsstrahlung-induced reactions as a probe of nucleon-nucleon correlations in heavy nuclei”. In: Proc. of 4-th Intern. Conf. NPAE-2012, p. 141, Kiev, Ukraine. Ref. [3]: S.A. Karamian, “To the mechanism of alpha particle emission induced by photons”. Submitted to Phys. Lett. B (2013).

6. 6 II. Inelastic acceleration of thermal neutrons by isomers Ref. [4]: S.A. Karamian and J.J. Carroll, “Cross section for inelastic neutron “acceleration” by 178m2 Hf”. Phys. Rev. C (2011) v. 83, p. 024604. Ref. [5]: O. Roig, G. Belier, et al., “Evidence for inelastic neutron acceleration by the 177 Lu isomer”. Phys. Rev. C (2006) v. 74, p. 054604. Ref. [6]. S.A. Karamian, A.G. Belov, et al., “Upper limit for 180m Ta depletion by neutrons”. In: Book of Abstracts of 63d Conf. on Nucl. Spectroscopy, Science, St-Petersburg, 2013.

7. 7 THRESHOLD DEPENDENCE OF THE ( ,n) AND ( ,p) REACTION YIELDS

8. 8 To systematize the spin dependence, the yields are plotted as a function of a new parameter: [I m (I m +1) – I t (I t + 1) ], where I m and I t are the spin values for the product isomer and the target nucleus. Choice of this parameter is very natural, despite somewhat new and original. The process probability in thermodynamics approach must be proportional to a number of microstates at definite thermal energy. Let’s remind the nuclear level density anzatz: This equation practically includes the subtraction of the rotational energy E rot ~ I(I + 1) from total excitation E* in order to get the thermal energy E therm = E* - E rot. The rotational energy could be considered as a form of kinetic energy. SPIN-DEPENDENCE: ISOMER YIELDS

9. 9 SYSTEMATIC OF YIELDS VERSUS “SPIN PARAMETER” 179 Hf ( ,p) 178m Lu 9/2 9 178m2 Hf ( ,n) 177m2 Hf 16 37/2 180m Ta ( ,p) 179m2 Hf 9 25/2

10. 10 ENCOUNTER DATA FOR THE ( , α) EXPERIMENT TargetAbundance, %ProductHalflifeE , keVBackground 109 Ag 48.2 105 Rh 35.4 h 319 105 Ag from (γ, 2n) 113 Cd 12.2 109 Pd 13.7 h 88 109 Cd from (γ, n) 115 In 95.7 111 Ag 7.45 d 342 – 119 Sn 8.6 115 Cd 53.4 h 528 – 137 Ba 11.2 133 Xe 5.25 d 81 133m Ba from (γ, n) 143 Nd 12.2 139 Ce 138 d 166 – 145 Nd 8.3 141 Ce 32.5 d 145 141 Nd from (γ, n) 153 Eu 52.2 149 Pm 53.1 h 286 149 Eu from (γ, 2n) 160 Gd 21.9 156 Sm 9.4 h 204 – 163 Dy 24.9 159 Gd 18.5 h 364 159 Dy from (γ, n) 176 Yb 12.8 172 Er 49.3 h 407 – 176 Lu 2.6 172 Tm 63.6 h 1094 172 Lu from (γ, 3n) 181 Ta 100 177 Lu 6.65 d 208 – 187 Re 62.6 183 Ta 5.1 d 246 183 Re from (γ, 2n) 193 Ir 62.7 189 Re 24.3 h 245 189 Ir from (γ, 2n) 203 Tl 29.5 199 Au 75.3 h 158 – 207 Pb 22.1 203 Hg 46.6 d 279 203 Pb from (γ, n)

11. 11 EXPERIMENTAL RESULTS FOR THE YIELD OF ( ,  ) REACTIONS TargetProductHalflifeE , keVRelative yield: ( ,  )/( ,n) Threshold parameter: (E th +B c ), MeV 109 Ag 105 Rh 35.4 h319(1.5 ±0.3)·10 –4 13.56 113 Cd 109 Pd 13.7 h88(2.4±0.3)·10 –4 14.32 115 In 111 Ag 7.45 d342(4.5±0.5)·10 –5 14.45 119 Sn 115 Cd 53.46 h528(3.9 ±0.4)·10 –5 15.31 176 Yb 172 Er 49.3 h407(0.4 ±0.1)·10 –5 14.75 181 Ta 177 Lu 6.65 d208(0.70 ±0.12)·10 –5 14.51 193 Ir 189 Re 24.3 h245≤ 2.8·10 –4 15.84 207 Pb 203 Hg 46.6 d279(1.7±0.2) ·10 –6 17.51

12. 12 MEASURED YIELDS OF THE ( , p) REACTIONS TargetReactionProductHalflifeE , keVRelative yield: ( , p)/( ,n) (E th +B c ), MeV nat Cd 112 Cd ( , p) 111 Ag7.45 d342(1.15±0.15)10 –2 14.83 113 Cd ( , p) 112 Ag3.12 h617(1.00±0.15)10 –2 14.89 114 Cd ( , p) 113 Ag5.37 h299(0.98±0.15)10 –2 15.40 nat Sn 118 Sn ( , p) 117g In43.2 min553 (4.9±0.5)10 –3 15.42 15.74 117m In116 min315 116 Sn ( , p) 115m In4.49 h336 (5.1±0.7)  10 -3 15.065 114 Sn ( , p) 113m In1.66 h392 (8.8 ±1.0)  10 -3 14.32 176 Yb 174 Yb ( , p) 173 Tm8.24 h399(0.75±0.15)10 –3 15.72 nat Hf 178 Hf ( , p) 177g Lu6.65 d208(1.8±0.4)10 –3 15.33

13. 13 RELATIVE YIELDS OF ( , p) AND ( ,  ) IN RATIO TO ( , n) REACTIONS AT E e =23 MEV VERSUS THRESHOLD PARAMETER VALUE.

14. 14 Z–DEPENDENCE OF THE ( ,  ) - REACTION YIELD. SOLID CURVE GIVES THE GUIDE FOR EYES.

15. 15 REACTION MECHANISM PATTERN 1 At low energy, ( ,  ) yield is suppressed, probably, due to the pre- formation factor same as in  decay; With 100 MeV protons, electrons, and photons, the pre-equilibrium exiton model is applicable: J.R.Wu and C.C.Chang, Phys.Rev., C17, 1540 (1978) – theory. Formation factor for  of about (10 -2 – 10 -3 ) is deduced from experiments. W.R.Dodge, et.al., Phys.Rev., C32, 781 (1985):  - yield by 20 times lower the proton emission; This model is hardly applicable to the case of 23 MeV bremsstrahlung. Free energy of about 5-7 MeV above  threshold does not allow generation of 4 excitons by photons; Conclusion: preformation factor as in  decay is preferable.

16. 16 REACTION MECHANISM PATTERN 2 1.Alpha-emission must be suppressed when no quasi-free α is available in a nucleus, but at the same time nucleons are ready for ejection; 2.Nucleons within the unexcited target nucleus are located and paired at definite orbits. They manifest themselves as non-interacting particles due to the Pauli principle; 3.In reactions with charged particles (HI), a strong impact of the projectile generates immediately a directed flow of perturbed nucleons and they could easily be joined together forming an α-cluster due to “Internal coalescence”.  HI

17. 17 SCHEME OF INNA PROCESS WITH THERMAL NEUTRONS

18. 18 INNA TRANSITIONS WITH 178m2 Hf AND 180m Ta

19. 19 CROSS SECTION OF THE INNA PROCESS (S 0 is ht S wave strength function)

20. 20 TRANSMISSION COEFFICIENTS T ℓj FOR NEUTRONS WITH ORBITAL MOMENTUM ℓ ( 178 Lu NUCLEUS)

21. 21 SINGLE PARTICLE LEVELS OF SHELL Internal orbital momentum of nucleons is great, like 5,6,7. N=107 ( 180 Ta)

22. 22 SUMMARY: MODIFICATION OF MECHANISM Centrifugal barrier allows emission of neutrons with minimum orbital momentum ℓ=0;1;2. Neutrons sitting at ℓ=3-7 orbits must proceed through the re- arrangement of orbital moments. So that, emission rate is suppressed and statistical decay widths are reduced. Possible process is virtual tunneling of a neutron pair with ℓ=0 and consequent pair break outside of the nucleus. One of neutrons remains inside nucleus and another one is emitted with high ℓ.