In spontaneous beta particle (β−1) emission, what is the source of emitted electron?
In spontaneous beta particle (β−1) emission, The nucleus is the source of emitted electron.
In electron capture, an electron orbiting around the nucleus combines with a nuclear proton to produce a neutron, which remains in the nucleus, and a neutrino, which is emitted.
Beta decay. In Beta decay a neutron changes into a proton plus an electron. The proton stays in the nucleus and the electron leaves the atom with high energy, and we call it a beta particle. When a beta particle is emitted from the nucleus the nucleus has one more proton and one less neutron. In beta decay of a nucleus, electrons are emitted. A beta particle is really just an electron. A neutron is the combination of an electron and a proton. When a nucleus decays, it will sometimes convert a neutron into a proton and eject the now free electron in the form of beta radiation.