Physics & Astronomy Publicationshttp://hdl.handle.net/1803/37722024-03-29T01:52:38Z2024-03-29T01:52:38ZSurface plasmon mediated harmonically resonant effects on third harmonic generation from Au and CuS nanoparticle filmsSpear, Nathan J.Yan, YuemingQueen, Joshua M.Singh, Mahi R.Macdonald, Janet E.Haglund, Richard F.http://hdl.handle.net/1803/180402023-03-01T19:29:50Z2023-01-19T00:00:00ZSurface plasmon mediated harmonically resonant effects on third harmonic generation from Au and CuS nanoparticle films
Spear, Nathan J.; Yan, Yueming; Queen, Joshua M.; Singh, Mahi R.; Macdonald, Janet E.; Haglund, Richard F.
A growing class of nonlinear materials employ the localized surface plasmonic resonance (LSPR) of nanoparticles to enhance harmonic generation. Material systems containing harmonically coupled metallic and semiconductor plasmonic nanoparticles have been shown to further increase performance. Here, we explore the effect of dual plasmonic interactions in bilayer CuS and Au nanoparticle films on third harmonic generation (THG). Detuning the CuS LSPR away from the excitation frequency changes the dominant upconversion pathway from THG to multiple photon photoluminescence (MPPL). Changing the size of the Au nanoparticle red shifts the LSPR from the second harmonic of the pump frequency and also eliminates the enhancement effect. When both LSPRs satisfy the harmonic condition, simultaneous excitation of CuS-Au nanoparticle films at the resonant frequency of each nanoparticle species enhances the generation of third harmonic light by sum-frequency generation, suggesting that the enhancement of THG in dually plasmonic nanoparticle films is the result of a cascaded nonlinear mechanism. An analytic model of the interaction between the plasmonic nanoparticles due to incoherent dipolar interactions is also presented. Understanding these processes opens a pathway for developing ultrafast, high-efficiency upconversion thin-film devices by clarifying the conditions that efficiently produce third harmonic generation without background MPPL or additional harmonics.
2023-01-19T00:00:00ZIndependent Validation of the Temperate Super-Earth HD 79211 b using HARPS-NStassun, Keivan G.http://hdl.handle.net/1803/180012023-02-20T21:39:38Z2023-02-01T00:00:00ZIndependent Validation of the Temperate Super-Earth HD 79211 b using HARPS-N
Stassun, Keivan G.
We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD79210 and HD79211, two M0V members of a gravitationally-bound binary system. We detect a planet candidate with a period of 24.421(-0.017)(+0.016) days around HD79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES and HIRES RVs spanning a total of 25 years, we further refine the planet candidate parameters to P = 24.422 +/- 0.014 days, K = 3.19 +/- 0.27 m s(-1), M sin i = 10.6 +/- 1.2M(circle plus), and a = 0.142 +/- 0.005 au. We do not find any additional planet candidate signals in the data of HD79211 nor do we find any planet candidate signals in HD79210. This system adds to the number of exoplanets detected in binaries with M dwarf members, and serves as a case study for planet formation in stellar binaries.
Only Vanderbilt University affiliated authors are listed on VUIR. For a full list of authors, access the version of record at https://iopscience.iop.org/article/10.3847/1538-3881/ac9ccd
2023-02-01T00:00:00ZBackscattering and Line Broadening in OrionO'Dell, C. R.Mendez-Delgado, J. E.http://hdl.handle.net/1803/179502023-02-20T17:27:06Z2022-12-19T00:00:00ZBackscattering and Line Broadening in Orion
O'Dell, C. R.; ; Mendez-Delgado, J. E.
Examination of emission lines in high-velocity-resolution optical spectra of the Orion Nebula confirms that the velocity component on the red wing of the main ionization front emission line is due to backscattering in the Photon Dominated Region. This scattered light component has a weak wavelength dependence that is consistent with either general interstellar medium particles or particles in the foreground of the Orion Nebula Cluster. An anomalous line-broadening component that has been known for 60+ years is characterized in unprecedented detail. Although this extra broadening may be due to turbulence along the line of sight of our spectra, we explore the possibility that it is due to Alfven waves in conditions where the ratio of magnetic and thermal energies are about equal and constant throughout the ionized gas.
Only Vanderbilt University affiliated authors are listed on VUIR. For a full list of authors, access the version of record at https://iopscience.iop.org/article/10.3847/1538-3881/ac9f44
2022-12-19T00:00:00ZA Low-mass Pre-main-sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESSStassun, Keivan G.Torres, GuillermoKounkel, MarinaFeliz, Dax L.Bouma, Luke G.Howell, Steve B.Gnilka, Crystal L.)Furlan, E.http://hdl.handle.net/1803/179362023-01-23T18:55:04Z2022-12-20T00:00:00ZA Low-mass Pre-main-sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESS
Stassun, Keivan G.; Torres, Guillermo; Kounkel, Marina; Feliz, Dax L.; Bouma, Luke G.; Howell, Steve B.; Gnilka, Crystal L.); Furlan, E.
We report the discovery of 2M1222-57 as a low-mass, pre-main-sequence (PMS) eclipsing binary (EB) in the Lower Centaurus Crux (LCC) association for which, using Gaia parallaxes and proper motions with a neural net age estimator, we determine an age of 16.2 +/- 2.2 Myr. The broadband spectral energy distribution (SED) shows clear excess at greater than or similar to 10 mu m indicative of a circumbinary disk, and new speckle imaging observations reveal a faint, tertiary companion separated by similar to 100 au. H alpha emission is modulated on the orbital period, consistent with theoretical models of orbitally pulsed accretion streams reaching from the inner disk edge to the central stars. From a joint analysis of spectroscopically determined radial velocities and TESS light curves, together with additional tight constraints provided by the SED and the Gaia parallax, we measure masses for the eclipsing stars of 0.74 M (circle dot) and 0.67 M (circle dot); radii of 0.98 R (circle dot) and 0.94 R (circle dot); and effective temperatures of 3750 K and 3645 K. The masses and radii of both stars are measured to an accuracy of similar to 1%. The measured radii are inflated, and the temperatures suppressed, relative to predictions of standard PMS evolutionary models at the age of LCC; also, the Li abundances are similar to 2 dex less depleted than predicted by those models. However, models that account for the global and internal effects of surface magnetic fields are able to simultaneously reproduce the measured radii, temperatures, and Li abundances at an age of 17.0 +/- 0.5 Myr. Altogether, the 2M1222-57 system presents very strong evidence that magnetic activity in young stars alters both their global properties and the physics of their interiors.
2022-12-20T00:00:00Z