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222. Cavity quantum electrodynamics with ferromagnetic magnons in a small yttrium-iron-garnet sphere

Author

Zhang, Dengke, Wang, Xin-Ming, Li, Tie-Fu, Luo, Xiao-Qing, Wu, Weidong, Nori, Franco, and You, J. Q.

Subjects
Quantum Physics, Condensed Matter - Materials Science
Abstract

Hybridizing collective spin excitations and a cavity with high cooperativity provides a new research subject in the field of cavity quantum electrodynamics and can also have potential applications to quantum information. Here we report an experimental study of cavity quantum electrodynamics with ferromagnetic magnons in a small yttrium-iron-garnet (YIG) sphere at both cryogenic and room temperatures. We observe for the first time a strong coupling of the same cavity mode to both a ferromagnetic-resonance (FMR) mode and a magnetostatic (MS) mode near FMR in the quantum limit. This is achieved at a temperature ~ 22 mK, where the average microwave photon number in the cavity is less than one. At room temperature, we also observe strong coupling of the cavity mode to the FMR mode in the same YIG sphere and find a slight increase of the damping rate of the FMR mode. These observations reveal the extraordinary robustness of the FMR mode against temperature. However, the MS mode becomes unobservable at room temperature in the measured transmission spectrum of the microwave cavity containing the YIG sphere. Our numerical simulations show that this is due to a drastic increase of the damping rate of the MS mode., Comment: 11 pages, 7 figures, 1 table

Published
2015
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240. Measuring OVOCs and VOCs by PTR-MS in an urban roadside microenvironment of Hong Kong: relative humidity and temperature dependence, and field intercomparisons

Author

Cui, Long, Zhang, Zhou, Huang, Yu, Lee, Shun Cheng, Blake, Donald Ray, Ho, Kin Fai, Wang, Bei, Gao, Yuan, Wang, Xin Ming, and Louie, Peter Kwok Keung

Subjects
Atmospheric Sciences, Meteorology & Atmospheric Sciences
Abstract

Abstract. Volatile organic compound (VOC) control is an important issue of air quality management in Hong Kong because ozone formation is generally VOC limited. Several oxygenated volatile organic compound (OVOC) and VOC measurement techniques – namely, (1) offline 2,4-dinitrophenylhydrazine (DNPH) cartridge sampling followed by high-performance liquid chromatography (HPLC) analysis; (2) online gas chromatography (GC) with flame ionization detection (FID); and (3) offline canister sampling followed by GC with mass spectrometer detection (MSD), FID, and electron capture detection (ECD) – were applied during this study. For the first time, the proton transfer reaction–mass spectrometry (PTR-MS) technique was also introduced to measured OVOCs and VOCs in an urban roadside area of Hong Kong. The integrated effect of ambient relative humidity (RH) and temperature (T) on formaldehyde measurements by PTR-MS was explored in this study. A Poly 2-D regression was found to be the best nonlinear surface simulation (r  =  0.97) of the experimental reaction rate coefficient ratio, ambient RH, and T for formaldehyde measurement. This correction method was found to be better than correcting formaldehyde concentrations directly via the absolute humidity of inlet sample, based on a 2-year field sampling campaign at Mong Kok (MK) in Hong Kong. For OVOC species, formaldehyde, acetaldehyde, acetone, and MEK showed good agreements between PTR-MS and DNPH-HPLC with slopes of 1.00, 1.10, 0.76, and 0.88, respectively, and correlation coefficients of 0.79, 0.75, 0.60, and 0.93, respectively. Overall, fair agreements were found between PTR-MS and online GC-FID for benzene (slope  =  1.23, r  =  0.95), toluene (slope  =  1.01, r  =  0.96) and C2-benzenes (slope  =  1.02, r  =  0.96) after correcting benzene and C2-benzenes levels which could be affected by fragments formed from ethylbenzene. For the intercomparisons between PTR-MS and offline canister measurements by GC-MSD/FID/ECD, benzene showed good agreement, with a slope of 1.05 (r  =  0.62), though PTR-MS had lower values for toluene and C2-benzenes with slopes of 0.78 (r  =  0.96) and 0.67 (r  =  0.92), respectively. All in all, the PTR-MS instrument is suitable for OVOC and VOC measurements in urban roadside areas.

Published
2016

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