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Earth can act as a transducer to convert ultralight bosonic dark matter (axions and hidden photons) into an oscillating magnetic field with a characteristic pattern across its surface. Here we describe the first results of a dedicated experiment, the Search for Noninteracting Particles Experimental Hunt, that aims to detect such dark-matter-induced magnetic-field patterns by performing correlated measurements with a network of magnetometers in relatively quiet magnetic environments (in the wilderness far from human-generated magnetic noise). Our experiment constrains parameter space describing hidden-photon and axion dark matter with Compton frequencies in the 0.5–5.0 Hz range. Limits on the kinetic-mixing parameter for hidden-photon dark matter represent the best experimental bounds to date in this frequency range. 

Abstract. The methanol extraction method was widely applied to isolate organic carbon(OC) from ambient aerosols, followed by measurements of brown carbon (BrC)absorption. However, undissolved OC fractions will lead to underestimatedBrC absorption. In this work, water, methanol (MeOH), MeOH / dichloromethane(MeOH / DCM, 1:1, v/v), MeOH / DCM (1:2, v/v), tetrahydrofuran (THF), andN,N-dimethylformamide (DMF) were tested for extraction efficiencies ofambient OC, and the light absorption of individual solvent extracts wasdetermined. Among the five solvents and solvent mixtures, DMF dissolved thehighest fractions of ambient OC (up to ∼95 %), followed byMeOH and MeOH / DCM mixtures (<90 %), and the DMF extracts hadsignificantly (p<0.05) higher light absorption than other solventextracts. This is because the OC fractions evaporating at highertemperatures (>280∘) are less soluble in MeOH(∼80 %) than in DMF (∼90 %) and containstronger light-absorbing chromophores. Moreover, the light absorption of DMFand MeOH extracts of collocated aerosol samples in Nanjing showed consistenttemporal variations in winter when biomass burning dominated BrC absorption, while the average light absorption of DMF extracts was more than 2 timesgreater than the MeOH extracts in late spring and summer. The average lightabsorption coefficient at 365 nm of DMF extracts was 30.7 % higher (p<0.01) than that of MeOH extracts. Source apportionment resultsindicated that the MeOH solubility of BrC associated with biomass burning,lubricating oil combustion, and coal combustion is similar to their DMFsolubility. The BrC linked with unburned fossil fuels and polymerizationprocesses of aerosol organics was less soluble in MeOH than in DMF, whichwas likely the main reason for the large difference in time series betweenMeOH and DMF extract absorption. These results highlight the importance oftesting different solvents to investigate the structures and lightabsorption of BrC, particularly for the low-volatility fraction potentiallyoriginating from non-combustion sources. 

We report the comparison of a series of 2D molecular crystals formed from the intermediates of the dehalogenation reaction of iodoethane versus various fluorinated iodoalkanes on Cu(111). High-resolution scanning tunneling microscopy enables us to distinguish the alkyl groups from the iodine atoms, and we find that the ethyl groups and iodine atoms formed from the dissociation of ethyl iodide are well mixed. However, fluorination of the alkyl tail changes this behavior and leads to local segregation of the two species on the surface. We postulate that the low-polarizability and relatively large dipole moment of the fluorinated species drive the ordered assemblies of the fluorinated alkyl species on the surface and discuss this in the context of how solvophobicity can drive the clustering of fluorinated groups and, hence, phase separation.