An official website of the United States government
Neutrinoless double beta decay is one of the most sensitive probes for new physics beyond the Standard Model of particle physics. One of the isotopes under investigation is , which would double beta decay into . Detecting the single daughter provides a sort of ultimate tool in the discrimination against backgrounds. Previous work demonstrated the ability to perform single atom imaging of Ba atoms in a single-vacancy site of a solid xenon matrix. In this paper, the effort to identify signal from individual barium atoms is extended to Ba atoms in a hexa-vacancy site in the matrix and is achieved despite increased photobleaching in this site. Abrupt fluorescence turn-off of a single Ba atom is also observed. Significant recovery of fluorescence signal lost through photobleaching is demonstrated upon annealing of Ba deposits in the Xe ice. Following annealing, it is observed that Ba atoms in the hexa-vacancy site exhibit antibleaching while Ba atoms in the tetra-vacancy site exhibit bleaching. This may be evidence for a matrix site transfer upon laser excitation. Our findings offer a path of continued research toward tagging of Ba daughters in all significant sites in solid xenon. Published by the American Physical Society2024
more »
« less
This content will become publicly available on April 1, 2026
Excitation and emission spectra of Ba+ ions in solid xenon
Excitation and emission spectra at 12 K temperature are presented for the first time for Ba+ in solid xenon. This is only the third such atomic ion studied in a solid noble gas matrix. Two groups of emission peaks, each with similar excitation spectra, photobleaching behavior and temperature dependence, are identified that may be associated with transitions from a common excited state in a particular solid xenon matrix site. Favorable conditions are found for imaging of single Ba+ ions in solid xenon, including reasonably strong emission efficiency, acceptable photobleaching and a method for overcoming background emission from the surface of the cooled sapphire window. A comparison of the new excitation spectrum of Ba+ in solid xenon with unpublished results on spectroscopy of Ba+ in liquid xenon helps confirm the identification of the latter.
more »
« less
- PAR ID:
- 10596635
- Publisher / Repository:
- Low Temperature Physics
- Date Published:
- Journal Name:
- Low Temperature Physics
- Volume:
- 51
- Issue:
- 4
- ISSN:
- 1063-777X
- Page Range / eLocation ID:
- 460 to 468
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The imaging of individual Ba2+ions in high pressure xenon gas is one possible way to attain background-free sensitivity to neutrinoless double beta decay and hence establish the Majorana nature of the neutrino. In this paper we demonstrate selective single Ba2+ion imaging inside a high-pressure xenon gas environment. Ba2+ions chelated with molecular chemosensors are resolved at the gas-solid interface using a diffraction-limited imaging system with scan area of 1 × 1 cm2located inside 10 bar of xenon gas. This form of microscopy represents key ingredient in the development of barium tagging for neutrinoless double beta decay searches in136Xe. This also provides a new tool for studying the photophysics of fluorescent molecules and chemosensors at the solid-gas interface to enable bottom-up design of catalysts and sensors.more » « less
-
The intrinsic fluorescence of bacterial samples has a proven potential for label-free bacterial characterization, monitoring bacterial metabolic functions, and as a mechanism for tracking the transport of relevant components through vesicles. The reduced scattering and axial confinement of the excitation offered by multiphoton imaging can be used to overcome some of the limitations of single-photon excitation (e.g., scattering and out-of-plane photobleaching) to the imaging of bacterial communities. In this work, we demonstrate in vivo multi-photon microscopy imaging of Streptomyces bacterial communities, based on the excitation of blue endogenous fluorophores, using an ultrafast Yb-fiber laser amplifier. Its parameters, such as the pulse energy, duration, wavelength, and repetition rate, enable in vivo multicolor imaging with a single source through the simultaneous two- and three-photon excitation of different fluorophores. Three-photon excitation at 1040 nm allows fluorophores with blue and green emission spectra to be addressed (and their corresponding ultraviolet and blue single-photon excitation wavelengths, respectively), and two-photon excitation at the same wavelength allows fluorophores with yellow, orange, or red emission spectra to be addressed (and their corresponding green, yellow, and orange single-photon excitation wavelengths). We demonstrate that three-photon excitation allows imaging over a depth range of more than 6 effective attenuation lengths to take place, corresponding to an 800 micrometer depth of imaging, in samples with a high density of fluorescent structures.more » « less
-
Abstract. Secondary organic aerosol (SOA) generated from the photooxidationof aromatic compounds in the presence of oxides of nitrogen (NOx) isknown to efficiently absorb ultraviolet and visible radiation. With exposureto sunlight, the photodegradation of chromophoric compounds in the SOAcauses this type of SOA to slowly photobleach. These photodegradationreactions may occur in cloud droplets, which are characterized by lowconcentrations of solutes, or in aerosol particles, which can have highlyviscous organic phases and aqueous phases with high concentrations ofinorganic salts. To investigate the effects of the surrounding matrix on therates and mechanisms of photodegradation of SOA compounds, SOA was preparedin a smog chamber by photooxidation of toluene in the presence of NOx.The collected SOA was photolyzed for up to 24 h using near-UV radiation(300–400 nm) from a xenon arc lamp under different conditions: directly onthe filter, dissolved in pure water, and dissolved in 1 M ammonium sulfate.The SOA mass absorption coefficient was measured as a function ofirradiation time to determine photobleaching rates. Electrospray ionizationhigh-resolution mass spectrometry coupled to liquid chromatographyseparation was used to observe changes in SOA composition resulting from theirradiation. The rate of decrease in SOA mass absorption coefficient due tophotobleaching was the fastest in water, with the presence of 1 M ammoniumsulfate modestly slowing down the photobleaching. By contrast,photobleaching directly on the filter was slower. The high-resolutionmass spectrometry analysis revealed an efficient photodegradation ofnitrophenol compounds on the filter but not in the aqueous phases, withrelatively little change observed in the composition of the SOA irradiatedin water or 1 M ammonium sulfate despite faster photobleaching than in theon-filter samples. This suggests that photodegradation of nitrophenolscontributes much more significantly to photobleaching in the organic phasethan in the aqueous phase. We conclude that the SOA absorption coefficientlifetime with respect to photobleaching and lifetimes of individualchromophores in SOA with respect to photodegradation will depend strongly onthe sample matrix in which SOA compounds are exposed to sunlight.more » « less
-
Several complexes of “PtL 2 ” composition containing two cyanoxime anions – 2-oximino-2-cyano- N -piperidineacetamide (PiPCO − ) and 2-oximino-2-cyano- N -morpholylacetamide (MCO − ) – have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL 2 ] n 1D polymers, while for the MCO − anion a red, solvent containing dimeric [Pt(MCO) 2 ·DMSO] 2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL 2 units are arranged into anisotropic extended solid [PtL 2 ] n polymers with the help of Pt⋯Pt metallophilic interactions. Crystal structures of monomeric PtL 2 (L = PiPCO − , MCO − ) and red dimeric [Pt(MCO) 2 ·DMSO] 2 complexes were determined and revealed the cis -arrangement of cyanoxime anions. The Pt–Pt distance in the “head-to-tail” red dimer was found to be 3.133 Å. The structure of the polymeric [Pt(PiPCO) 2 ] n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 Å intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt( iii ) species. Both pure dark-green [PtL 2 ] n polymers showed a considerable room temperature electrical conductivity of 20–30 S cm −1 , which evidences the formation of a mixed valence Pt( ii )/Pt( iv ) system. We discovered that these 1D polymeric [PtL 2 ] n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL 2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL 2 ] n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence “metal wires” held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL 2 ] n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL 2 ] n in the −190–+60 °C range was studied as well.more » « less
