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1.
F. Hindle G. Mouret S. Eliet M. Guinet A. Cuisset R. Bocquet T. Yasui D. Rovera 《Applied physics. B, Lasers and optics》2011,104(4):763-768
The generation of cw-THz radiation by photomixing is particularly suited to the high resolution spectroscopy of gases; nevertheless,
until recently, it has suffered from a lack of frequency metrology. Frequency combs are a powerful tool that can transfer
microwave frequency standards to optical frequencies and a single comb has permitted accurate (10−8) THz frequency synthesis with a limited tuning range. A THz synthesizer composed of three extended cavity laser diodes phase
locked to a frequency comb has been constructed and its utility for high resolution gas phase spectroscopy demonstrated. The
third laser diode allows a larger tuning range of up to 300 MHz to be achieved without the need for large frequency excursions,
while the frequency comb provides a versatile link to be established from any traceable microwave frequency standard. The
use of a single frequency comb as a reference for all of the cw-lasers eliminates the dependency of synthesized frequency
on the carrier envelope offset frequency. This greatly simplifies the frequency comb stabilization requirements and leads
to a reduced instrument complexity. 相似文献
2.
Parthey CG Matveev A Alnis J Bernhardt B Beyer A Holzwarth R Maistrou A Pohl R Predehl K Udem T Wilken T Kolachevsky N Abgrall M Rovera D Salomon C Laurent P Hänsch TW 《Physical review letters》2011,107(20):203001
We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10) Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb. 相似文献
3.
I.?Courtillot A.?Quessada-Vial A.?Brusch D.?Kolker G. D.?Rovera P.?LemondeEmail author 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,33(2):161-171
We report the frequency measurement with an accuracy in the
100 kHz range of several optical transitions of atomic Sr:
1S0-3P1 at 689 nm, 3P1-3S1 at 688 nm and
3P0-3S1 at 679 nm. Measurements are performed with a
frequency chain based on a femtosecond laser referenced to primary
frequency standards. They allowed the indirect determination with
a 70 kHz uncertainty of the frequency of the doubly forbidden
transition of 87Sr at 698 nm and
in a second step its direct observation. Frequency measurements
are performed for 88Sr and 87Sr, allowing the
determination of 3P0, 3P1 and 3S1 isotope shifts, as
well as the 3S1 hyperfine constants. 相似文献
4.
5.
V. Pomel J. C. Rovera A. Godard F. Marsais G. Quguiner 《Journal of heterocyclic chemistry》1996,33(6):1995-2005
Starting from available 2-amino-6-chloro-3-nitropyridine, synthesis of 3-amino-6-pyridinecarboxylic acid derivatives precursor for pyridine ring C of streptonigrin analogues is described. 相似文献
6.
Philippe Kalck René Poilblanc Antoine Gaset Alain Rovera R.P. Martin 《Tetrahedron letters》1980,21(5):459-462
We describe a method to anchor dinuclear rhodium(I) complexes by substitution of the chlorine bridge in Rh2(μ-Cl)2L4 with LiSR where R represents a polymeric chain. The catalytic activity of such complexes compares well with that observed in homogeneous phase. 相似文献
7.
The photodynamic activities of novel asymmetrically meso-substituted cationic porphyrins, 5,10-di(4-methylphenyl)-15,20-di(4-trimethylammoniumphenyl)porphyrin iodide 1 and 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide 2 and its metal complex with Pd(II) 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram-negative bacterium Escherichia coli. The amphiphilic character of porphyrin 2 was increased by the presence of a high-lipophilic trifluoromethyl group and its photophysical properties changed by forming a complex with Pd(II). Absorption and fluorescence spectroscopic studies were compared in different media. Fluorescence quantum yields (phi(F)) of 0.16 for 1 in tetrahydrofuran and 0.08 for 2 in N, N-dimethylformamide (DMF) were calculated, whereas no significant emission was detected for Pd(II) porphyrin 3. The singlet molecular oxygen, O(2)((1)Delta(g)), production was evaluated using 9,10-dimethylanthracene in DMF yielding relative values of 1, 0.55 and 0.47 for porphyrins 3, 2 and 1, respectively. A faster decomposition of l-tryptophan was obtained using Pd(II) porphyrin 3 as sensitizer with respect to the free-base porphyrins 1 and 2. In biological medium, the behavior of cationic porphyrins 1-3 were compared with that of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin 4, which was used as a noncationic sensitizer. These porphyrins are rapidly bound to E. coli cells in 5 min and the amount of cell-bound sensitizer is not appreciably changed incubating the cultures for longer times. The recovered porphyrin 2 after one washing step reaches a value of approximately 2.9 nmol/10(6) cells and this amount remains high even after three washes, indicating that this sensitizer is tightly bound to cells. Photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. In both cases, a higher photoinactivation of cells was found for tricationic porphyrin 2 and 3, causing a approximately 5.5 log (99.999%) decrease of cell survival, when treated with 10 microM of sensitizer. Under these conditions, a lower effect was found for porphyrin 1 (approximately 4 log) whereas sensitizer 4 did not produce appreciable photodamage. The results were also confirmed by growth delay experiments. These studies show that the amphiphilic tricationic porphyrin 2 and 3 bearing a trifluoromethyl group can be a promising model for phototherapeutic agents with potential applications in inactivation of bacteria by photodynamic therapy. 相似文献
8.
The isotopic frequency shift for the 3P1-3P0Δmj=0 fine structure transition in the first metastable triplet of 24Mg and 26Mg is reported. The transitions corresponding to the two even isotopes of Mg have been observed via the fluorescence emission at 4571 Å of the intercombination line 3P1-1P0 in a metastable atomic beam. The center frequencies have been measured with an uncertainty of 7×10-9; the isotopic shift turned out to be 1706 ± 2 kHz. 相似文献
9.
The pressure shift of the mF:0 → 0 microwave transition of the cesium ground state has been measured for seven buffer gases (He, Ne, N2, CH4, C2H6, C3H8, C4H10). The high resolution of the experimental apparatus (about one part in 1011 also allows an accurate measurement of the temperature dependence of the shift. 相似文献
10.
X. Baillard M. Fouché R. Le Targat P. G. Westergaard A. Lecallier F. Chapelet M. Abgrall G. D. Rovera P. Laurent P. Rosenbusch S. Bize G. Santarelli A. Clairon P. Lemonde G. Grosche B. Lipphardt H. Schnatz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):11-17
We present a new evaluation of an 87Sr optical lattice clock using spin polarized atoms. The frequency of the
1S0→3P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional uncertainty of
2.6×10-15, a value that is comparable to the frequency difference between the various primary standards throughout the
world. This measurement is in excellent agreement with a previous one of similar accuracy [Phys. Rev. Lett. 98, 083002 (2007)]. 相似文献