440 8 Nuclear Physics – II
8.44 For neutrons with kinetic energy 100 MeV incident on nuclei with mass num-
berA=120, the real and imaginary parts of the complex potential are approx-
imately−25 and−10 MeV, respectively. On the basis of these data, estimate
(i) the deBroglie wavelength of the neutron inside the nucleus
(ii) the probability that the neutron is absorbed in passing through the nucleus
8.2.10 Nuclear Reactions (General).........................
8.45^13 N is a positron emitter with an end point energy of 1.2 MeV. Determine the
threshold of the reactionp+^13 C→^13 N+n, if the neutron – hydrogen atom
mass difference is 0.78 MeV.
[Osmania University 1964]
8.46 The reaction, p+^73 Li→^74 Be+n, is known to be endothermic by 1.62 MeV.
Find the total energy released when^7 Be decays by K capture and calculate the
energy carried off by the neutrino and recoil nucleus, respectively.
(Mpc^2 = 938 .23 MeV,Mnc^2 = 939 .52 MeV,Mec^2 = 0 .51 MeV)
[University of Bristol 1960]
8.47 If a target nucleus has mass number 24 and a level at 1.37 MeV excita-
tion, what is the minimum proton energy required to observe scattering from
this level.
[Osmania University 1966]
8.48 The nuclear reaction which results from the incidence of sufficiently energetic
α-particles on nitrogen nuclei is^42 He+^147 N→X+^11 H. What is the decay
product X? What is the minimumα-particle kinetic energy (in the laboratory
frame) required to initiate the above reaction?
(Atomic masses in amu:^1 H=^1 .0081;^4 He=^4 .0039;^14 N=^14 .0075; X=
17 .0045)
[University of Manchester]
8.49 The Q values for the reactions^2 H(d,n)^3 He and^2 H(d,p)^3 H are 3.27 MeV and
4.03 MeV, respectively. Show that the difference between the binding energy
of the^3 H nucleus and that of the^3 He nucleus is 0.76 MeV and verify that this
is approximately the magnitude of Coulomb energy due to the two protons of
the^3 He nucleus. (Distance between the protons in the nucleus 3^1 /^3 × 1 .3fm).
[University of London 1968]
8.50 Thermal neutrons are captured by^105 Btoform^115 B which decays byα-particle
emission to Li. Write down the reaction equation and calculate
(a) The Q-Value of the decay in MeV
(b) The Kinetic energy of theα-particles in MeV.
(Atomic masses:^105 B= 10 .01611 amu;^10 n= 1 .008987 amu;^73 Li
= 7 .01822 amu;^42 He= 4 .003879 amu; 1 amu=931 MeV)
[University of Bristol 1967]