text: The hindrance factor compares the theoretical and experimental rates of this process.
full_question: The hindrance factor compares the theoretical and experimental rates of this process. The natural logarithm of the rate of this process is linearly related to Z over the square root of kinetic energy. This process occurs near the upper-right end of the belt of stability. A model of this process, based on quantum tunneling through a potential well from the strong force, replicated the empirical Geiger-Nuttall Law and was proposed by (*) George Gamow. This process is the source of ionizers used in smoke detectors. This phenomenon gives diagonal movement on a plot of A versus Z in the thorium chain. It decreases the mass number by four, the atomic number by two, and releases a helium nucleus. For 10 points, name this form of radioactive decay contrasted with beta decay.
first_sentence: The hindrance factor compares the theoretical and experimental rates of this process.
raw_answer: alpha decay [or alpha emission; prompt on radioactive decay or radioactivity]