Oral Presentations - Session 1C: UC 330
Atomic Structure Determinations for Neutron-Capture Elemental Ions
Presentation Type
Presentation
Faculty Mentor’s Full Name
David Macaluso
Faculty Mentor’s Department
Physics & Astronomy
Abstract / Artist's Statement
Neutron-capture (n-capture) elements are formed when the nucleus of a particular element absorbs a neutron, leaving the nucleus in highly excited and unstable state. This excited nucleus then decays in one of several possible pathways which can ultimately produce a new element where the number of protons has increased by one. These elements have recently been detected for the first time in astrophysical objects, so their chemical evolution is largely unknown. Determining the abundance of n-capture elements in astrophysical objects would facilitate a deeper understanding of the chemical evolution of the Universe. To further study these elements, information regarding the “energy-dependent photoionization cross-sections” for each element is necessary. These cross sections are a measure of the probability that an electron will be ejected from the atom after it absorbs a high energy photon. Data has been collected at the Advanced Light Source at Lawrence Berkeley National Laboratory for several atomic species, including Rb+ and Br2+, analysis of which are the emphases of this research project. One important goal of the analysis is to identify the complex auto-ionization resonance features of the spectrum. When these resonances are closely related, they can form what is known as a Rydberg series, which is a series of peaks that decrease in height from low to high energy and can function as a highly accurate probe of the energy levels of the atom. Each series’ energy is a function of quantum mechanical restrictions and multiple physical variables. By adjusting the many variables in the computer program Origin, precise series identifications for Rb+ and Br2+ were obtained.
Atomic Structure Determinations for Neutron-Capture Elemental Ions
UC 330
Neutron-capture (n-capture) elements are formed when the nucleus of a particular element absorbs a neutron, leaving the nucleus in highly excited and unstable state. This excited nucleus then decays in one of several possible pathways which can ultimately produce a new element where the number of protons has increased by one. These elements have recently been detected for the first time in astrophysical objects, so their chemical evolution is largely unknown. Determining the abundance of n-capture elements in astrophysical objects would facilitate a deeper understanding of the chemical evolution of the Universe. To further study these elements, information regarding the “energy-dependent photoionization cross-sections” for each element is necessary. These cross sections are a measure of the probability that an electron will be ejected from the atom after it absorbs a high energy photon. Data has been collected at the Advanced Light Source at Lawrence Berkeley National Laboratory for several atomic species, including Rb+ and Br2+, analysis of which are the emphases of this research project. One important goal of the analysis is to identify the complex auto-ionization resonance features of the spectrum. When these resonances are closely related, they can form what is known as a Rydberg series, which is a series of peaks that decrease in height from low to high energy and can function as a highly accurate probe of the energy levels of the atom. Each series’ energy is a function of quantum mechanical restrictions and multiple physical variables. By adjusting the many variables in the computer program Origin, precise series identifications for Rb+ and Br2+ were obtained.