This study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a continuous X-ray has interesting and useful statistical properties. The total photoionization production...This study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a continuous X-ray has interesting and useful statistical properties. The total photoionization production is linearly propor- tional to the time duration of the laser pulse and the square of the beam size. The spectral double energy-integration is an intrinsic value of the laser-assisted X-ray photoionization, which linearly depends on the laser intensity and which quantita- tively reflects the strengths of the laser-field modulation and the quantum interference between photoelectrons. The spectral energy width also linearly depends on the laser intensity. These linear relationships suggest new methods for the in-situ measurement of laser intensity and pulse duration with high precision.展开更多
We report a discovery that an intense few-cycle laser pulse passing through gas leaves a fingerprint of its field en- velope on the photoelectron energy spectrum, which involves continuous X-ray radiations. The spectr...We report a discovery that an intense few-cycle laser pulse passing through gas leaves a fingerprint of its field en- velope on the photoelectron energy spectrum, which involves continuous X-ray radiations. The spectrum resulting from the photoionization processes includes significant quantum enhancement and interference and exhibits interesting energetic properties. The spectral cut-off energies reflect the strength, time, and interference of the laser field modulation on the photoelectron energy. These energetic properties suggest a new method for precise intense-laser-pulse measurement in situ. The method has the advantages of accuracy, simplicity, speed, and large dynamic ranges （up to many orders of intensity）.展开更多
Ultra-thin α-Fe2O3（hematite） films have been deposited by radio frequency（RF） sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power an...Ultra-thin α-Fe2O3（hematite） films have been deposited by radio frequency（RF） sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow（argon）,the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 VRHE.Addition of small amounts of O2to the sputter gas improved the photoactivity significantly.展开更多
The effects of N+ implantation under various conditions on CVD diamond films were analyzed with Raman spectroscopy, four-point probe method, X-ray diffraction (XRD), Rutherford backseattering spectroscopy (RBS), ultra...The effects of N+ implantation under various conditions on CVD diamond films were analyzed with Raman spectroscopy, four-point probe method, X-ray diffraction (XRD), Rutherford backseattering spectroscopy (RBS), ultraviolet photoluminescence spectroscopy (UV-PL), Fourier transformation infrared absorption spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the N+ implantation doping without any graphitization has been successfully realized when 100 keV N+ ions at a dosage of 2 × 1016 cm-2 were implanted into diamond films at 550℃ . UV-PL spectra indicate that the implanted N+ ions formed an electrically inactive deep-level impurity in diamond films. So the sheet resistance of the sample after N+ implantation changed little. Carbon nitride containing C≡N covalent bond has been successfully synthesized by 100 keV, 1.2×1018 N/cm2 N+ implantation into diamond films. Most of the implanted N+ ions formed C≡N covalent bonds with C atoms. The others were free state nitrogen, which existed in the excessive nitrogen layers. C(1s) XPS studies show the existence of three different C(1s) bonding states, corresponding to graphite, i-carbon and the carbon of C≡N covalent bonding state, respectively, which agrees well with the Raman results.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11175010)
文摘This study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a continuous X-ray has interesting and useful statistical properties. The total photoionization production is linearly propor- tional to the time duration of the laser pulse and the square of the beam size. The spectral double energy-integration is an intrinsic value of the laser-assisted X-ray photoionization, which linearly depends on the laser intensity and which quantita- tively reflects the strengths of the laser-field modulation and the quantum interference between photoelectrons. The spectral energy width also linearly depends on the laser intensity. These linear relationships suggest new methods for the in-situ measurement of laser intensity and pulse duration with high precision.
基金The National Natural Science Foundation of China(90922035)the Knowledge Innovation Program of the Chinese Academy of Sciences(KJCX2-EW-H03)Fujian High Technology Research and Development Program(2012H0046)
基金supported by the National Natural Science Foundation of China(Grant No.11175010)
文摘We report a discovery that an intense few-cycle laser pulse passing through gas leaves a fingerprint of its field en- velope on the photoelectron energy spectrum, which involves continuous X-ray radiations. The spectrum resulting from the photoionization processes includes significant quantum enhancement and interference and exhibits interesting energetic properties. The spectral cut-off energies reflect the strength, time, and interference of the laser field modulation on the photoelectron energy. These energetic properties suggest a new method for precise intense-laser-pulse measurement in situ. The method has the advantages of accuracy, simplicity, speed, and large dynamic ranges （up to many orders of intensity）.
基金supported by the German Federal Ministry of Education and Research (BMBF) under contract#03SF0353A"H_2-NanoSolar"
文摘Ultra-thin α-Fe2O3（hematite） films have been deposited by radio frequency（RF） sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow（argon）,the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 VRHE.Addition of small amounts of O2to the sputter gas improved the photoactivity significantly.
文摘The effects of N+ implantation under various conditions on CVD diamond films were analyzed with Raman spectroscopy, four-point probe method, X-ray diffraction (XRD), Rutherford backseattering spectroscopy (RBS), ultraviolet photoluminescence spectroscopy (UV-PL), Fourier transformation infrared absorption spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the N+ implantation doping without any graphitization has been successfully realized when 100 keV N+ ions at a dosage of 2 × 1016 cm-2 were implanted into diamond films at 550℃ . UV-PL spectra indicate that the implanted N+ ions formed an electrically inactive deep-level impurity in diamond films. So the sheet resistance of the sample after N+ implantation changed little. Carbon nitride containing C≡N covalent bond has been successfully synthesized by 100 keV, 1.2×1018 N/cm2 N+ implantation into diamond films. Most of the implanted N+ ions formed C≡N covalent bonds with C atoms. The others were free state nitrogen, which existed in the excessive nitrogen layers. C(1s) XPS studies show the existence of three different C(1s) bonding states, corresponding to graphite, i-carbon and the carbon of C≡N covalent bonding state, respectively, which agrees well with the Raman results.
