Richard Greco - Academia.edu (original) (raw)

Papers by Richard Greco

Cornell University - arXiv, May 13, 2009

We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric sta... more We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229 Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229 Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solidstate optical frequency reference that surpasses the precision of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision of 3 × 10 −17 < ∆f /f < 1 × 10 −15 after 1 s of photon collection may be achieved with a systematic-limited accuracy of ∆f /f ∼ 2 × 10 −16. Improvement by 10 2 − 10 3 of the constraints on the variability of several important fundamental constants also appears possible.

AIP Conference Proceedings, 2001

ABSTRACT It has been found that metals in woody tissue will influence the growth rate of trees. U... more ABSTRACT It has been found that metals in woody tissue will influence the growth rate of trees. Utilization of particle induced x-ray emission (PIXE) for determination of trace element levels in biological systems is rather extensive. In this work, three rings taken from a 50-year-old Yellow Pine tree were PIXE analyzed with minimal sample preparation. Eight elements (potassium, calcium, titanium, chromium, manganese, iron, copper, and zinc) were studied during the PIXE analysis. The relationship between relative yield and tree ring thickness is presented for each detected element. These results show that wood taken from the oldest ring has the widest ring thickness and possesses the largest quantities of all the tested elements. Calcium appears to have the largest relative yield of all the tested elements and is roughly proportional to ring thickness. Heavier elements, such as lead and mercury, were not detected in any of the Yellow Pine samples.

There has been considerable interest in measuring heavy metal pollution, such as mercury, using t... more There has been considerable interest in measuring heavy metal pollution, such as mercury, using tree ring analysis. Since 1970, this method has provided a historical snapshot of pollutant concentrations near hazardous waste sites. Traditional methods of analysis have long been used with heavy metal pollutants such as mercury. These methods, such as atomic fluorescence and laser ablation, are sometimes time

Emerging Lithographic Technologies IX, 2005

High Energy Focused Ion Beam (HEFIB) direct writing is proving to be an attractive and powerful m... more High Energy Focused Ion Beam (HEFIB) direct writing is proving to be an attractive and powerful maskless lithography technique for production of high aspect ratio 3-D microstructures in polymer resists and semiconductors. HEFIB with Proton beam (P-beam writing) offers several unique advantages for microfabrication applications: (a) the focused beam is scanned directly across the sample (no mask), (b) the range

International Journal of PIXE, 2003

Several southern magnolia (magnolia grandiflora) tree samples, with known concentrations of mercu... more Several southern magnolia (magnolia grandiflora) tree samples, with known concentrations of mercury, were analyzed using particle induced x-ray emission (PIXE) and neutron activation analysis (NAA). Results from the PIXE measurements indicate that the average mercury absorption percentage was found to be 85 ± 4%. The distribution of mercury was found to be reasonably homogeneous over the sample surface. However, small variations in mercury concentration are most likely caused by the structure of cellulose in the wood. Mercury in the samples appears to be stable to a total integrated charge of 10 μC. Three mercury L-shell x-rays are easily observed in the resulting PIXE spectrum. Using PIXE, the mercury detection limit was calculated to be approximately 1 ppm. With one exception, the measured NAA mercury concentrations were larger than the corresponding mass-based values. The NAA mercury detection limit for the southern magnolia samples was estimated to be about 0.017 ppm (17 ppb).

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

... KeV–MeV energetic Au and Xe irradiation in Si(1 0 0), Si(1 1 0), n-type via masked, patterned... more ... KeV–MeV energetic Au and Xe irradiation in Si(1 0 0), Si(1 1 0), n-type via masked, patterned resists (SU(8)) have created layers in Si, resistant to ... [9] B. Rout, RD Greco, AD Dymnikov, JR Reinhardt, J. Peeples, M. Kamal, M. Lentz, GA Glass, in: R. Scott Mackay (Ed.), Emerging ...

MRS Proceedings, 2005

An overview of the present state of high energy focused ion beam (HEFIB) system technology, nanop... more An overview of the present state of high energy focused ion beam (HEFIB) system technology, nanoprobe system design and specific ion beam writing applications will be presented. In particular, the combination of P-beam, heavy-ion writing and ion implantation to produce microstructures in resists and silicon will be demonstrated.Heretofore, the development of HEFIB technology worldwide has progressed through a series of developments at independent research facilities, each having relatively narrow and mostly isolated, research purposes. However, a complete, versatile HEFIB nanoprobe system capable of both analysis and modification will require the combination of several component systems, each with specialized technology, and significant advances in the design of a complete system can only be expected from an effort that includes a coordinated development of the component parts.

Physical Review Letters, 2010

We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric sta... more We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229 Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229 Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solid-state optical frequency reference that surpasses the short-term stability of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision (short-term stability) of 3 Â 10 À17 < Áf=f < 1 Â 10 À15 after 1 s of photon collection may be achieved with a systematic-limited accuracy (long-term stability) of Áf=f $ 2 Â 10 À16. Improvement by 10 2 À 10 3 of the constraints on the variability of several important fundamental constants also appears possible.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005

Development of stable high brightness ion sources with accelerators will enhance the capabilities... more Development of stable high brightness ion sources with accelerators will enhance the capabilities for micro-analysis as well as the micro-fabrication. Recently we have upgraded a Duoplasmatron ion source associated with a 1.7 MV tandem (NEC, Pelletron) accelerator to produce high brightness proton beam for nuclear microprobe application at the Louisiana Accelerator Center. This has substantially increased the ion source life time as well as the accelerator beam brightness. The beam brightness was found to be highly heterogeneous, with paraxial rays about an order of magnitude brighter than surrounding rays.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005

The term “P-beam writing” is used to describe the technique of using focused high energy proton m... more The term “P-beam writing” is used to describe the technique of using focused high energy proton microbeams for micro or nanofabrication applications. The P-beam technique can be used to rapidly fabricate three-dimensional, high aspect ratio microstructures in a variety ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006

Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used ... more Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used to create layers resistant to KOH wet etching. Microscale patterns were produced in PMMA and SU(8) resist coatings on the silicon substrates using P-beam writing and developed. The silicon substrates were subsequently exposed using 1.5 MeV Au 3+ ions with fluences as high as 1 • 10 16 ions/cm 2 and additional patterns were exposed using copper scanning electron microscope calibration grids as masks on the silicon substrates. When wet etched with KOH microstructures were created in the silicon due to the resistance to KOH etching cause by the Au implantation. The process of combining the fabrication of masked patterns with P-beam writing with broad beam Au implantation through the masks can be a promising, cost-effective process for nanostructure engineering with Si.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

For high accuracy in energy-depth conversion in channeling Rutherford backscattering spectrometry... more For high accuracy in energy-depth conversion in channeling Rutherford backscattering spectrometry (RBS) analysis, the precise knowledge of the channeling stopping powers of helium ions in crystalline solids is demanded. Here, we propose a novel approach to ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002

An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituent... more An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituents in terrestrial organic matter during the early coalification process. The artificial coal is produced by subjecting the peat to incremental increases in temperature up to 60 °C and pressures to 14.48 MPa over a four-week period in a partially open reactor. A standard polished thin section

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010

ABSTRACT

Journal of Nuclear Materials, 2009

Radiation induced mechanical property changes can cause major difficulties in designing systems o... more Radiation induced mechanical property changes can cause major difficulties in designing systems operating in a radiation environment. Investigating these mechanical property changes in an irradiation environment is a costly and time consuming activity. Ion beam accelerator experiments have the advantage of allowing relatively fast and inexpensive materials irradiations without activating the sample but do in general not allow large beam penetration depth into the sample. In this study, the ferritic/martensitic steel HT-9 was processed and heat treated to produce one specimen with a large grained ferritic microstructure and further heat treated to form a second specimen with a fine tempered martensitic lath structure and exposed to an ion beam and tested after irradiation using nanoindentation to investigate the irradiation induced changes in mechanical properties. It is shown that the HT-9 in the ferritic heat treatment is more susceptible to irradiation hardening than HT-9 after the tempered martensitic heat treatment. Also at an irradiation temperature above 550°C no detectable hardness increase due to irradiation was detected. The results are also compared to data from the literature gained from the fast flux test facility.

Journal of Nuclear Materials, 2008

Developing and qualifying nuclear materials have traditionally been a very costly enterprise that... more Developing and qualifying nuclear materials have traditionally been a very costly enterprise that often takes a decade or longer. The bottleneck has been the need to test materials under extreme conditions, where long irradiations times have been required. A irradiation and corrosion experiment (ICE) facility is introduced which uses low energy proton irradiation and enables testing of materials under a wide range of different conditions and environments with the benefit of relatively quick tests, low sample activation, efficiency and low cost, and the ability to obtain a wide range of data from one sample. These data can be compared to data gained from neutron irradiation experiments. Supplement to extreme conditions in nuclear reactors, this dedicated experiment will allow fast materials testing and basic studies in order to get a quicker and better understanding of the materials behavior in different environments under irradiation. We present the basic experimental design, experimental testing, and first operational experience.

Journal of Nuclear Materials, 2009

Ta and Ta-1% W are being considered to be used as target clad materials in the LANSCE proton beam... more Ta and Ta-1% W are being considered to be used as target clad materials in the LANSCE proton beam line for the material test station (MTS). To investigate the embrittlement of these materials due to oxygen contamination and proton irradiation, Ta and Ta-1 wt% W (as received and with $400 ppm O) were exposed to a 3.5 MeV proton beam at the ion beam materials laboratory at LANL. After irradiating the samples in the proton beam, nanoindentation was performed in cross-section to investigate the hardness increase of the materials due to irradiation. The nanoindentation showed that the hardness increase due to irradiation is between 9% and 20% depending on the material. The results show good agreement with mechanical testing results on tantalum and Ta-1 wt% W after high energy proton irradiation to doses up to 23 dpa.

Journal of Luminescence, 2013

Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer... more Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer transition Report Title The nucleus of the thorium-229 isotope possesses a first excited nuclear state (229mTh) at an exceptionally low energy of 7.8±0.5 eV above the nuclear ground state (229gTh), as determined by earlier indirect measurements. This is the only nuclear excited state known that is within the range of optical spectroscopy. This paper reports progress toward detecting the 229mTh state directly by luminescence spectroscopy in the vacuum ultraviolet spectral region. The estimated natural linewidth of the 229gTh?229mTh isomer transition of 2?×0.1 to 2?×10 mHz is expected to broaden to ?10 kHz for 229Th4+ doped into a suitable crystal. The factors governing the choice of crystal system and the substantial challenges in acquiring a sufficiently large quantity of 229Th are discussed. We show that the 229gTh?229mTh transition energy can be identified to within 0.1 nm by luminescence excitation and luminescence spectroscopy using the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. This would open the door for subsequent laser-based measurements of the isomer transition and future applications of 229Th in nuclear clocks. We also show that 233U-doped materials should produce an intrinsic, continuous, and sufficiently high rate of 229mTh?229gTh luminescence and could be a useful aid in the initial direct search of the isomer transition. Optical spectroscopy of an atomic nucleus: Prog Approved for public release; distribution is unlimited.

Cornell University - arXiv, May 13, 2009

We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric sta... more We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229 Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229 Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solidstate optical frequency reference that surpasses the precision of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision of 3 × 10 −17 < ∆f /f < 1 × 10 −15 after 1 s of photon collection may be achieved with a systematic-limited accuracy of ∆f /f ∼ 2 × 10 −16. Improvement by 10 2 − 10 3 of the constraints on the variability of several important fundamental constants also appears possible.

AIP Conference Proceedings, 2001

ABSTRACT It has been found that metals in woody tissue will influence the growth rate of trees. U... more ABSTRACT It has been found that metals in woody tissue will influence the growth rate of trees. Utilization of particle induced x-ray emission (PIXE) for determination of trace element levels in biological systems is rather extensive. In this work, three rings taken from a 50-year-old Yellow Pine tree were PIXE analyzed with minimal sample preparation. Eight elements (potassium, calcium, titanium, chromium, manganese, iron, copper, and zinc) were studied during the PIXE analysis. The relationship between relative yield and tree ring thickness is presented for each detected element. These results show that wood taken from the oldest ring has the widest ring thickness and possesses the largest quantities of all the tested elements. Calcium appears to have the largest relative yield of all the tested elements and is roughly proportional to ring thickness. Heavier elements, such as lead and mercury, were not detected in any of the Yellow Pine samples.

There has been considerable interest in measuring heavy metal pollution, such as mercury, using t... more There has been considerable interest in measuring heavy metal pollution, such as mercury, using tree ring analysis. Since 1970, this method has provided a historical snapshot of pollutant concentrations near hazardous waste sites. Traditional methods of analysis have long been used with heavy metal pollutants such as mercury. These methods, such as atomic fluorescence and laser ablation, are sometimes time

Emerging Lithographic Technologies IX, 2005

High Energy Focused Ion Beam (HEFIB) direct writing is proving to be an attractive and powerful m... more High Energy Focused Ion Beam (HEFIB) direct writing is proving to be an attractive and powerful maskless lithography technique for production of high aspect ratio 3-D microstructures in polymer resists and semiconductors. HEFIB with Proton beam (P-beam writing) offers several unique advantages for microfabrication applications: (a) the focused beam is scanned directly across the sample (no mask), (b) the range

International Journal of PIXE, 2003

Several southern magnolia (magnolia grandiflora) tree samples, with known concentrations of mercu... more Several southern magnolia (magnolia grandiflora) tree samples, with known concentrations of mercury, were analyzed using particle induced x-ray emission (PIXE) and neutron activation analysis (NAA). Results from the PIXE measurements indicate that the average mercury absorption percentage was found to be 85 ± 4%. The distribution of mercury was found to be reasonably homogeneous over the sample surface. However, small variations in mercury concentration are most likely caused by the structure of cellulose in the wood. Mercury in the samples appears to be stable to a total integrated charge of 10 μC. Three mercury L-shell x-rays are easily observed in the resulting PIXE spectrum. Using PIXE, the mercury detection limit was calculated to be approximately 1 ppm. With one exception, the measured NAA mercury concentrations were larger than the corresponding mass-based values. The NAA mercury detection limit for the southern magnolia samples was estimated to be about 0.017 ppm (17 ppb).

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

... KeV–MeV energetic Au and Xe irradiation in Si(1 0 0), Si(1 1 0), n-type via masked, patterned... more ... KeV–MeV energetic Au and Xe irradiation in Si(1 0 0), Si(1 1 0), n-type via masked, patterned resists (SU(8)) have created layers in Si, resistant to ... [9] B. Rout, RD Greco, AD Dymnikov, JR Reinhardt, J. Peeples, M. Kamal, M. Lentz, GA Glass, in: R. Scott Mackay (Ed.), Emerging ...

MRS Proceedings, 2005

An overview of the present state of high energy focused ion beam (HEFIB) system technology, nanop... more An overview of the present state of high energy focused ion beam (HEFIB) system technology, nanoprobe system design and specific ion beam writing applications will be presented. In particular, the combination of P-beam, heavy-ion writing and ion implantation to produce microstructures in resists and silicon will be demonstrated.Heretofore, the development of HEFIB technology worldwide has progressed through a series of developments at independent research facilities, each having relatively narrow and mostly isolated, research purposes. However, a complete, versatile HEFIB nanoprobe system capable of both analysis and modification will require the combination of several component systems, each with specialized technology, and significant advances in the design of a complete system can only be expected from an effort that includes a coordinated development of the component parts.

Physical Review Letters, 2010

We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric sta... more We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229 Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229 Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solid-state optical frequency reference that surpasses the short-term stability of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision (short-term stability) of 3 Â 10 À17 < Áf=f < 1 Â 10 À15 after 1 s of photon collection may be achieved with a systematic-limited accuracy (long-term stability) of Áf=f $ 2 Â 10 À16. Improvement by 10 2 À 10 3 of the constraints on the variability of several important fundamental constants also appears possible.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005

Development of stable high brightness ion sources with accelerators will enhance the capabilities... more Development of stable high brightness ion sources with accelerators will enhance the capabilities for micro-analysis as well as the micro-fabrication. Recently we have upgraded a Duoplasmatron ion source associated with a 1.7 MV tandem (NEC, Pelletron) accelerator to produce high brightness proton beam for nuclear microprobe application at the Louisiana Accelerator Center. This has substantially increased the ion source life time as well as the accelerator beam brightness. The beam brightness was found to be highly heterogeneous, with paraxial rays about an order of magnitude brighter than surrounding rays.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005

The term “P-beam writing” is used to describe the technique of using focused high energy proton m... more The term “P-beam writing” is used to describe the technique of using focused high energy proton microbeams for micro or nanofabrication applications. The P-beam technique can be used to rapidly fabricate three-dimensional, high aspect ratio microstructures in a variety ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006

Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used ... more Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used to create layers resistant to KOH wet etching. Microscale patterns were produced in PMMA and SU(8) resist coatings on the silicon substrates using P-beam writing and developed. The silicon substrates were subsequently exposed using 1.5 MeV Au 3+ ions with fluences as high as 1 • 10 16 ions/cm 2 and additional patterns were exposed using copper scanning electron microscope calibration grids as masks on the silicon substrates. When wet etched with KOH microstructures were created in the silicon due to the resistance to KOH etching cause by the Au implantation. The process of combining the fabrication of masked patterns with P-beam writing with broad beam Au implantation through the masks can be a promising, cost-effective process for nanostructure engineering with Si.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007

For high accuracy in energy-depth conversion in channeling Rutherford backscattering spectrometry... more For high accuracy in energy-depth conversion in channeling Rutherford backscattering spectrometry (RBS) analysis, the precise knowledge of the channeling stopping powers of helium ions in crystalline solids is demanded. Here, we propose a novel approach to ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002

An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituent... more An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituents in terrestrial organic matter during the early coalification process. The artificial coal is produced by subjecting the peat to incremental increases in temperature up to 60 °C and pressures to 14.48 MPa over a four-week period in a partially open reactor. A standard polished thin section

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010

ABSTRACT

Journal of Nuclear Materials, 2009

Radiation induced mechanical property changes can cause major difficulties in designing systems o... more Radiation induced mechanical property changes can cause major difficulties in designing systems operating in a radiation environment. Investigating these mechanical property changes in an irradiation environment is a costly and time consuming activity. Ion beam accelerator experiments have the advantage of allowing relatively fast and inexpensive materials irradiations without activating the sample but do in general not allow large beam penetration depth into the sample. In this study, the ferritic/martensitic steel HT-9 was processed and heat treated to produce one specimen with a large grained ferritic microstructure and further heat treated to form a second specimen with a fine tempered martensitic lath structure and exposed to an ion beam and tested after irradiation using nanoindentation to investigate the irradiation induced changes in mechanical properties. It is shown that the HT-9 in the ferritic heat treatment is more susceptible to irradiation hardening than HT-9 after the tempered martensitic heat treatment. Also at an irradiation temperature above 550°C no detectable hardness increase due to irradiation was detected. The results are also compared to data from the literature gained from the fast flux test facility.

Journal of Nuclear Materials, 2008

Developing and qualifying nuclear materials have traditionally been a very costly enterprise that... more Developing and qualifying nuclear materials have traditionally been a very costly enterprise that often takes a decade or longer. The bottleneck has been the need to test materials under extreme conditions, where long irradiations times have been required. A irradiation and corrosion experiment (ICE) facility is introduced which uses low energy proton irradiation and enables testing of materials under a wide range of different conditions and environments with the benefit of relatively quick tests, low sample activation, efficiency and low cost, and the ability to obtain a wide range of data from one sample. These data can be compared to data gained from neutron irradiation experiments. Supplement to extreme conditions in nuclear reactors, this dedicated experiment will allow fast materials testing and basic studies in order to get a quicker and better understanding of the materials behavior in different environments under irradiation. We present the basic experimental design, experimental testing, and first operational experience.

Journal of Nuclear Materials, 2009

Ta and Ta-1% W are being considered to be used as target clad materials in the LANSCE proton beam... more Ta and Ta-1% W are being considered to be used as target clad materials in the LANSCE proton beam line for the material test station (MTS). To investigate the embrittlement of these materials due to oxygen contamination and proton irradiation, Ta and Ta-1 wt% W (as received and with $400 ppm O) were exposed to a 3.5 MeV proton beam at the ion beam materials laboratory at LANL. After irradiating the samples in the proton beam, nanoindentation was performed in cross-section to investigate the hardness increase of the materials due to irradiation. The nanoindentation showed that the hardness increase due to irradiation is between 9% and 20% depending on the material. The results show good agreement with mechanical testing results on tantalum and Ta-1 wt% W after high energy proton irradiation to doses up to 23 dpa.

Journal of Luminescence, 2013

Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer... more Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer transition Report Title The nucleus of the thorium-229 isotope possesses a first excited nuclear state (229mTh) at an exceptionally low energy of 7.8±0.5 eV above the nuclear ground state (229gTh), as determined by earlier indirect measurements. This is the only nuclear excited state known that is within the range of optical spectroscopy. This paper reports progress toward detecting the 229mTh state directly by luminescence spectroscopy in the vacuum ultraviolet spectral region. The estimated natural linewidth of the 229gTh?229mTh isomer transition of 2?×0.1 to 2?×10 mHz is expected to broaden to ?10 kHz for 229Th4+ doped into a suitable crystal. The factors governing the choice of crystal system and the substantial challenges in acquiring a sufficiently large quantity of 229Th are discussed. We show that the 229gTh?229mTh transition energy can be identified to within 0.1 nm by luminescence excitation and luminescence spectroscopy using the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. This would open the door for subsequent laser-based measurements of the isomer transition and future applications of 229Th in nuclear clocks. We also show that 233U-doped materials should produce an intrinsic, continuous, and sufficiently high rate of 229mTh?229gTh luminescence and could be a useful aid in the initial direct search of the isomer transition. Optical spectroscopy of an atomic nucleus: Prog Approved for public release; distribution is unlimited.