Введение
Ядерный распад, в котором атомное ядро излучает небольшой кластер нейтронов и протонов.
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number Ad = A − Ae and atomic number Zd = Z − Ze, where Ae = Ne + Ze. For example:
Radium 223 → Carbon 14 + Lead 209
This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for all such isotopes. The branching ratio with respect to alpha decay is rather small (see the Table below). Ta and Tc are the half lives of the parent nucleus relative to alpha decay and cluster radioactivity, respectively. Cluster decay, like alpha decay, is a quantum tunneling process: in order to be emitted, the cluster must penetrate a potential barrier. This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically. In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum
where Ad is the mass number of the daughter, Ad = A − Ae. Cluster decay exists in an intermediate position between alpha decay (in which a nucleus spits out a 4He nucleus), and spontaneous fission, in which a heavy nucleus splits into two (or more) large fragments and an assorted number of neutrons. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay. In cluster decay for a given radioisotope, the emitted particle is a light nucleus and the decay method always emits this same particle. For heavier emitted clusters, there is otherwise practically no qualitative difference between cluster decay and spontaneous cold fission.
Кластерный распад, также называемый радиоактивностью тяжелых частиц, радиоактивностью тяжелых ионов или тяжелым кластерным распадом, является редким типом ядерного распада, в котором атомное ядро излучает небольшой "кластер" нейтронов и протонов, содержащий больше нуклонов, чем альфа-частица, но меньше, чем типичный фрагмент бинарного деления. Третичное деление на три фрагмента также приводит к образованию продуктов, сопоставимых по размеру с кластерами. Потеря протонов из родительского ядра приводит к образованию ядра другого элемента, дочернего ядра, с массовым числом Ad = A − Ae и атомным номером Zd = Z − Ze, где Ae = Ne + Ze. Например:
Радий-223 → Углерод-14 + Свинец-209.
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number Ad = A − Ae and atomic number Zd = Z − Ze, where Ae = Ne + Ze. For example:
Radium 223 → Carbon 14 + Lead 209
This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for all such isotopes. The branching ratio with respect to alpha decay is rather small (see the Table below). Ta and Tc are the half lives of the parent nucleus relative to alpha decay and cluster radioactivity, respectively. Cluster decay, like alpha decay, is a quantum tunneling process: in order to be emitted, the cluster must penetrate a potential barrier. This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically. In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum
where Ad is the mass number of the daughter, Ad = A − Ae. Cluster decay exists in an intermediate position between alpha decay (in which a nucleus spits out a 4He nucleus), and spontaneous fission, in which a heavy nucleus splits into two (or more) large fragments and an assorted number of neutrons. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay. In cluster decay for a given radioisotope, the emitted particle is a light nucleus and the decay method always emits this same particle. For heavier emitted clusters, there is otherwise practically no qualitative difference between cluster decay and spontaneous cold fission.
Этот тип редкого режима распада наблюдается у радиоизотопов, которые преимущественно распадаются посредством альфа-распада, и он встречается лишь в небольшом проценте всех распадов для таких изотопов. Отношение ветвления по отношению к альфа-распад довольно мало (см. таблицу ниже). Ta и Tc – это периоды полураспада родительского ядра относительно альфа-распада и кластерного распада соответственно. Кластерный распад, как и альфа-распад, является процессом квантового туннелирования: для того чтобы быть испущенным, кластер должен пройти через потенциальный барьер. Этот процесс отличается от более случайного ядерного распада, который предшествует испусканию легких фрагментов при троичном делении, которое может быть результатом ядерной реакции, но также может быть типом спонтанного радиоактивного распада в определенных нуклидах, демонстрируя, что для деления не обязательно требуется входная энергия, что делает его принципиально отличным механизмом. В отсутствие потерь энергии на деформацию и возбуждение фрагментов, как в явлениях холодного деления или при альфа-распаде, полная кинетическая энергия равна Q-значению и распределяется между частицами обратно пропорционально их массам, в соответствии с законом сохранения импульса.
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number Ad = A − Ae and atomic number Zd = Z − Ze, where Ae = Ne + Ze. For example:
Radium 223 → Carbon 14 + Lead 209
This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for all such isotopes. The branching ratio with respect to alpha decay is rather small (see the Table below). Ta and Tc are the half lives of the parent nucleus relative to alpha decay and cluster radioactivity, respectively. Cluster decay, like alpha decay, is a quantum tunneling process: in order to be emitted, the cluster must penetrate a potential barrier. This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically. In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum
where Ad is the mass number of the daughter, Ad = A − Ae. Cluster decay exists in an intermediate position between alpha decay (in which a nucleus spits out a 4He nucleus), and spontaneous fission, in which a heavy nucleus splits into two (or more) large fragments and an assorted number of neutrons. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay. In cluster decay for a given radioisotope, the emitted particle is a light nucleus and the decay method always emits this same particle. For heavier emitted clusters, there is otherwise practically no qualitative difference between cluster decay and spontaneous cold fission.
где Ad – массовое число дочернего ядра, Ad = A − Ae. Кластерный распад занимает промежуточное положение между альфа-распадом (при котором ядро испускает ядро гелия-4) и спонтанным делением, при котором тяжелое ядро расщепляется на два (или более) крупных фрагмента и некоторое количество нейтронов. Спонтанное деление приводит к вероятностному распределению дочерних продуктов, что отличает его от кластерного распада. При кластерном распаде для данного радиоизотопа испускаемая частица является легким ядром, и метод распада всегда приводит к испусканию именно этой частицы. Для более тяжелых испускаемых кластеров практически нет качественной разницы между кластерным распадом и спонтанным холодным делением.
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number Ad = A − Ae and atomic number Zd = Z − Ze, where Ae = Ne + Ze. For example:
Radium 223 → Carbon 14 + Lead 209
This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for all such isotopes. The branching ratio with respect to alpha decay is rather small (see the Table below). Ta and Tc are the half lives of the parent nucleus relative to alpha decay and cluster radioactivity, respectively. Cluster decay, like alpha decay, is a quantum tunneling process: in order to be emitted, the cluster must penetrate a potential barrier. This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically. In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum
where Ad is the mass number of the daughter, Ad = A − Ae. Cluster decay exists in an intermediate position between alpha decay (in which a nucleus spits out a 4He nucleus), and spontaneous fission, in which a heavy nucleus splits into two (or more) large fragments and an assorted number of neutrons. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay. In cluster decay for a given radioisotope, the emitted particle is a light nucleus and the decay method always emits this same particle. For heavier emitted clusters, there is otherwise practically no qualitative difference between cluster decay and spontaneous cold fission.
Прекрасная структура
Мелкая структура в радиоактивности 14C ядра 223Ra впервые была обсуждена М. Грейнером и В. Шейдом в 1986 году. Сверхпроводящий спектрометр SOLENO Института физики ядерных реакций (IPN) в Орсе используется с 1984 года для идентификации 14C кластеров, испускаемых ядрами 222–224,226Ra. Кроме того, он был использован для обнаружения этой мелкой структуры, наблюдая переходы к возбужденным состояниям дочернего ядра. Подтвержден предсказанный в [указании на источник] переход с возбужденным состоянием 14C: основной сферический компонент деформированной волновой функции родительского ядра имеет характер i11/2, то есть основной компонент является сферическим.
the fine structure observing transitions to excited states of the daughter. A transition with an excited state of 14C predicted in Ref. was confirmed: the main spherical component of the deformed parent wave function has an i11/2 character, i. e. the main component is spherical.