A diamond-shaped shock wave was created in a helium arcjet plasma. Visi- ble/ultraviolet emission spectroscopy was used to investigate the condition for the formation of stable shocks and to determine characteristics ...A diamond-shaped shock wave was created in a helium arcjet plasma. Visi- ble/ultraviolet emission spectroscopy was used to investigate the condition for the formation of stable shocks and to determine characteristics of the plasma. Dependence of the position of the shock front on the gas pressure in the expansion region was investigated. It was found that the shock wave arises from the collision of plasma particles and residual neutral atoms in that region. Continuum and line spectra of neutral helium were measured, from which the electron temper- atures were derived. The electron density was deduced from the Inglis-Teller limit of the He I 2p3p-3d3D series. The temperature and density were found to have almost constant values of 0.2 eV and 8.5x 1013 cm-3, respectively, across the shock front.展开更多
An investigation has been made on the adsorption and decomposition of formic acid on slightly oxidized Nb(110)surface(0/Nb atom ratio=0.2)using high resolution electron energy loss spectroscopy(HREELS),and a correspon...An investigation has been made on the adsorption and decomposition of formic acid on slightly oxidized Nb(110)surface(0/Nb atom ratio=0.2)using high resolution electron energy loss spectroscopy(HREELS),and a corresponding surface reaction mode is given.At 140 K,formic acid of low exposure on such an Nb(110)surface decomposed to formate,which bonded on Nb in monodentate configuration,simultaneously some formate decomposed to CO,which adsorbed on the surface.Formic acid multilayers formed when the exposure was high.While the temperature was increased to above 190 K,multilayer formic acid desorbed,and the surface was covered with mon-odentate-bonded formate and CO.In the temperature range of 250-300 K,chemisorbed formate changed from monodentate configuration into bridging configuration and CO molecules disappeared.The decomposition of formate at higher temperatures led to the oxidation of Nb.The formate formed in the high exposure case was so stable that it did not decompose even the temperature was as high as 540 K.展开更多
文摘A diamond-shaped shock wave was created in a helium arcjet plasma. Visi- ble/ultraviolet emission spectroscopy was used to investigate the condition for the formation of stable shocks and to determine characteristics of the plasma. Dependence of the position of the shock front on the gas pressure in the expansion region was investigated. It was found that the shock wave arises from the collision of plasma particles and residual neutral atoms in that region. Continuum and line spectra of neutral helium were measured, from which the electron temper- atures were derived. The electron density was deduced from the Inglis-Teller limit of the He I 2p3p-3d3D series. The temperature and density were found to have almost constant values of 0.2 eV and 8.5x 1013 cm-3, respectively, across the shock front.
基金supported by the National Natural Science Foundation of China
文摘An investigation has been made on the adsorption and decomposition of formic acid on slightly oxidized Nb(110)surface(0/Nb atom ratio=0.2)using high resolution electron energy loss spectroscopy(HREELS),and a corresponding surface reaction mode is given.At 140 K,formic acid of low exposure on such an Nb(110)surface decomposed to formate,which bonded on Nb in monodentate configuration,simultaneously some formate decomposed to CO,which adsorbed on the surface.Formic acid multilayers formed when the exposure was high.While the temperature was increased to above 190 K,multilayer formic acid desorbed,and the surface was covered with mon-odentate-bonded formate and CO.In the temperature range of 250-300 K,chemisorbed formate changed from monodentate configuration into bridging configuration and CO molecules disappeared.The decomposition of formate at higher temperatures led to the oxidation of Nb.The formate formed in the high exposure case was so stable that it did not decompose even the temperature was as high as 540 K.
