More Like this

1. Fine-structure Transitions of Ne ⁺ , Ar ⁺ , Ne ²⁺ , and Ar ²⁺ Induced by Collisions with Atomic Hydrogen

   https://doi.org/10.3847/1538-4357/ad0e77  

   Yan, Pei-Gen; Babb, James F (January 2024, The Astrophysical Journal)

   Abstract We calculate cross sections for fine-structure transitions of Ne⁺, Ar⁺, Ne²⁺, and Ar²⁺in collisions with atomic hydrogen by using quantum-mechanical methods. Relaxation rate coefficients are calculated for temperatures up to 10,000 K. The temperature-dependent critical densities for the relaxation of Ne⁺, Ar⁺, Ne²⁺, and Ar²⁺in collisions with H have been determined and compared to the critical densities for collisions with electrons. The present calculations will be useful for studies utilizing the infrared lines [Neii] 12.8, [Neiii] 15.6, [Neiii] 36.0, [Arii] 6.99, [Ariii] 8.99, and [Ariii] 21.8μm as diagnostics of, for example, planetary nebulae and star formation. 

   more » « less
2. Enabling Visible Light Sensitization of Yb ^III , Nd ^III and Er ^III in Dimeric Ln ^III /Ga ^III Metallacrowns through Functionalization with Ru ^II Complexes for NIR‐II Multiplex Imaging

   https://doi.org/10.1002/anie.202416101  

   Bădescu‐Singureanu, Codruţa_C; Nizovtsev, Anton_S; Pecoraro, Vincent_L; Petoud, Stéphane; Eliseeva, Svetlana_V (November 2024, Angewandte Chemie International Edition)

   Abstract Multiplex imaging in the second near‐infrared window (NIR‐II, 1000–1700 nm) provides exciting opportunities for more precise understanding of biological processes and more accurate diagnosis of diseases by enabling real‐time acquisition of images with improved contrast and spatial resolution in deeper tissues. Today, the number of imaging agents suitable for this modality remains very scarce. In this work, we have synthesized and fully characterized, including theoretical calculations, a series of dimeric Ln^III/Ga^IIImetallacrowns bearing Ru^IIpolypyridyl complexes,LnRu‐3(Ln=Y^III, Yb^III, Nd^III, Er^III). Relaxed structures ofYRu‐3in the ground and the excited electronic states have been calculated using dispersion‐corrected density functional theory methods. Detailed photophysical studies ofLnRu‐3have demonstrated that characteristic emission signals of Yb^III, Nd^IIIand Er^IIIin the NIR‐II range can be sensitized upon excitation in the visible range through Ru^II‐centered metal‐to‐ligand charge transfer (MLCT) states. We have also showed that these NIR‐II signals are unambiguously detected in an imaging experiment using capillaries and biological tissue‐mimicking phantoms. This work opens unprecedented perspectives for NIR‐II multiplex imaging using Ln^III‐based molecular compounds. 

   more » « less
3. Spectroscopic study of the 4f ⁷ 6s ^{2 8} S 7/2∘ – 4f ⁷ ( ⁸ S ^° ) 6s6p( ¹ P ^° ) ⁸ P _5/2,7/2 transitions in neutral europium-151 and europium-153: absolute frequency and hyperfine structure

   https://doi.org/10.1364/JOSAB.521181  

   Maruko, C.; Çölmek, N_N; Herd, M_T; Ahrendsen, K_J; Cabrales, B.; Cannon, G.; Davis, E.; Guo, X_Y; Karani, T.; Wallace, A.; et al (April 2024, Journal of the Optical Society of America B)

   We report on spectroscopic measurements on the 4f⁷6s²⁸S_7/2^∘−4f⁷(⁸S^∘)6s6p(¹P^∘)⁸P_5/2,7/2transitions at 466.32 nm and 462.85 nm, respectively, in neutral europium-151 and europium-153. The center of gravity frequencies for the 151 and 153 isotopes for both transitions are reported for the first time using saturated absorption spectroscopy. For the 6s6p(¹P^∘)⁸P_5/2state, the center of gravity frequencies were found to be 642,894,493.3(4) MHz and 642,891,693.3(9) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−157.01(3)MHz,B(151)=74.5(4)MHz andA(153)=−69.43(14)MHz,B(153)=191.0(26)MHz. These hyperfine values are all consistent with previously published results except forB(151) that has a small discrepancy. The isotope shift was found to be 2799.54(20) MHz, a small discrepancy with previously published results. For the 6s6p(¹P^∘)⁸P_7/2state, the center of gravity frequencies were found to be 647,708,930.6(6) MHz and 647,705,958.4(26) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−218.66(4)MHz,B(151)=−293.4(8)MHz andA(153)=−97.15(13)MHz,B(153)=−750(3)MHz. These values are all consistent with previously published results except forA(151) that has a small discrepancy. The isotope shift was found to be 2972.8(5) MHz, a small discrepancy with previously measured results. 

   more » « less
4. Reimagining e⁺e⁻ collider precision luminosity measurements

   https://doi.org/10.1051/epjconf/202431501024  

   Wilson, Graham; Madison, Brendon (December 2024, EPJ Web of Conferences)

   Jeans, D; Tian, J (Ed.)

   Our recent work has shown that a novel much higher granularity forward calorimetry concept can enable much more detailed and precise reconstruction than the baseline designs based on LEP luminometers, along with the capability of electron/positron/photon separation. This new calorimeter concept is designed primarily to maximize the acceptance for e⁺e⁻→ γγ as an alternative luminosity process, where it serves to define the inner edge of the acceptance (there is no outer edge, as the complete detector is used in the measurement), while continuing to provide the standard luminosity measurement from small-angle Bhabha scattering (SABS). It will also serve as a general forward electromagnetic calorimeter helping ensure hermeticity and detecting individual electrons, positrons, and photons. In this contribution we highlight the Bhabha rejection capability in the context of the e⁺e⁻→ γγ luminosity measurement and motivate the utility of a Bhabha “mini-tracker” consisting of a few planes of upstream thin silicon detectors. This could further refine the e⁺/e⁻polar angle measurement, aid with charge measurement, improve Bhabha rejection (for γγ), and, last-but-not-least, help mitigate the beam-induced electromagnetic deflection that biases the Bhabha acceptance by providing high precision longitudinal vertex information in Bhabha events, which can be used to diagnose this effect of the beam on the final-state electron and positron. 

   more » « less
5. Understanding Soap Formation in Paint Films by ²⁰⁷Pb, ¹¹⁹Sn, and ¹³C Solid-State NMR

   Catalano, J.; Yao, Y.; Murphy, A.; Zumbulyadis, N.; Centeno, S.A.; Dybowski, C. (October 2014, Materials science and technology)

   The formation of lead carboxylates (lead soaps) has been identified as the cause of deterioration of hundreds of oil paintings. Soaps form when heavy metal-containing pigments, for example lead white and lead-tin yellow, react with saturated fatty acids in the oil medium. Understanding the mechanism of the reactions requires chemical information, which can be obtained with solid-state ²⁰⁷Pb, ¹¹⁹Sn and ¹³C NMR spectroscopy. Using the chemical-shift tensors determined by solid-state NMR we can gain structural insights on the coordination environment of the lead carboxylates and identify and quantify components in a paint film mixture. We have examined the spectroscopy of lead-containing pigments, lead carboxylates, and model paint films that were subjected to accelerated aging. We have also begun to investigate the dynamics of soap formation by ¹³C NMR spectroscopy. The NMR methods applied to the model paint systems could also be applied to other lead-containing materials. 

   more » « less