6.2 W laser-diode end-pumped continuous-wave Nd:YALO3 laser at 1.34 μm

We report a compact and efficient LD end-pumped linearly polarized Nd:YAP laser operating at 1.34 μm. The laser system with different crystal lengths, output couplers and cavity types were compared. Based on optimizing of the pump system and laser cavity, 6.2 W laser radiation at 1341.4 nm with c-axis polarized was achieved, corresponding to an optical conversion efficiency of about 24.8% with respect to the incident pump power. The laser threshold was only about 1.3 W and the optical slope efficiency was up to 27.2%.     

Characterization of pure high-grade DCIS on magnetic resonance imaging using the evolving breast MR lexicon terminology: can it be differentiated from pure invasive disease?

Magnetic resonance imaging (MRI) is now a recognized method of imaging the breast. Unfortunately, there is lack of standardization in the MRI terminology used to characterize the appearance of breast lesions. Moreover, cases of mixed histologies are often imaged. We retrospectively identified cases of pure high-grade ductal carcinoma in situ (DCIS) using the recently introduced breast MRI lexicon and characterized the lesions in order to try and identify features that might distinguish high-grade DCIS from invasive disease. Five-year review of our institution's database revealed 637 patients underwent gadolinium-enhanced breast MRI examination. Twenty patients had histologically proven pure high-grade DCIS. After excluding patients with previous chemotherapy or inadequate MRI examination, 13 patients were analyzed and compared to the 13 most recent cases of pure invasive breast carcinoma. The morphological and dynamic features were then compared. High-grade DCIS cases were significantly more likely to show focal branching pattern (P=.03) and to have an irregular contour (P=.03), compared with invasive disease. Although of marginal statistical significance, DCIS lesions are more likely to have a lower morphological score than invasive carcinoma (P=.06), whilst the latter is more likely to show ring enhancement (P=.07). Use of breast MRI for staging at our institution shows that pure DCIS and pure invasive cancers are both rare entities. Despite the relatively limited numbers, we identified features that would help to differentiate high-grade DCIS from invasive carcinoma on MRI.     

High sensitivity absorption spectroscopy of methane at 80 K in the 1.58 μm transparency window: Temperature dependence and importance of the CH3D contribution

The high resolution absorption spectrum of methane in the 1.58 μm transparency window has been recorded at room temperature and at 79 K by CW-Cavity Ring Down Spectroscopy using a cryogenic cell and a series of Distributed Feed Back (DFB) diode lasers. The achieved sensitivity (α_min ∼ 3 × 10⁻¹⁰ cm⁻¹) has allowed for a detailed characterization of the 6289-6526 cm⁻¹ region which corresponds to the lowest opacity of the transparency window. A list of 6868 and 4555 transitions with intensities as weak as 1 × 10⁻²⁹ cm/molecule was constructed from the recordings at 297 and 79 K, respectively. By comparison with a spectrum of CH₃D recorded separately by Fourier Transform Spectroscopy, 1282 and 640 transitions of monodeuterated methane, CH₃D, in natural abundance in our sample were identified at 297 and 79 K, respectively.The rotational temperature determined from the intensity distribution of the 3ν₂ band of CH₃D (79.3 K) was found in good agreement with the temperature value previously obtained from the Doppler line broadening. The reduction of the rotational congestion by cooling down to 79 K reveals a spectral region near 6300 cm⁻¹ where CH₃D transitions are dominant.The low energy values of the transitions observed both at 79 K and at room temperature were derived from the variation of their line intensities. These transitions with lower energy determination represent 93.9% and 68.4% of the total absorbance in the region, at 79 K and room temperature, respectively. The quality of the obtained empirical low energy values is demonstrated for CH₄ by the marked propensity of the empirical low J values to be close to integers. The line lists at 79 K and room temperature provided as Supplementary Material allow accounting for the temperature dependence of methane absorption between these two temperatures. The investigated region covering the 5ν₄ band of the ¹²CH₄ isotopologue will be valuable for the theoretical treatment of this band which is the lowest energy band of the icosad.     

Formation of γ-Fe2O3 hierarchical nanostructures at 500 °C in a high magnetic field

Three-dimensional (3-D) hierarchical nanostructures of γ-Fe₂O₃ are prepared by a solvothermal process combined with subsequent thermal treatment in air at 500 or 350 °C with the aid of a high magnetic field. The experimental results indicate that γ-Fe₂O₃ instead of α-Fe₂O₃ forms in air at 500 °C in a 12 T field. The products are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetization curves measured at room temperature exhibit superparamagnetic characteristics.     

Cryogenic absorption cells operating inside a Bruker IFS-125HR: First results for CH4 at 7 μm

New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of ±0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200-1800 cm⁻¹ spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the ν₄ fundamental band of ¹³CH₄ indicated that an empirical power law used for the temperature dependence of the N₂-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17] and [18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.     

The 2ν3 band of CH4 revisited with line mixing: Consequences for spectroscopy and atmospheric retrievals at 1.67 μm

This paper presents a study of absorption in N₂-broadened P and R manifolds of the 2ν₃ band of CH₄ near 6000 cm⁻¹ using high resolution laboratory and atmospheric spectra. This region is of prime importance for the retrieval of methane abundances in the Earth's atmosphere using ground-based or space-borne spectrometers. Recent laboratory investigations have been devoted to the methane spectroscopic parameters in this band, motivated by their previous poor knowledge and their increasing use by remote sensing experiments. In the absence of a better model, previous studies have used Voigt line shapes and thus purposely neglected line mixing (LM). In this paper, we first present direct comparisons between measured laboratory spectra and the results of a model which accounts for LM without adjusting any of the spectroscopic parameters. A good agreement is obtained and the results show that LM does have a significant influence on the shapes of P and R manifolds. Hence, most previously observed discrepancies were not due to improper broadening and shifting coefficients but to the neglect of this effect. This also confirms that widths and shifts derived in recent 2ν₃ band studies neglecting LM are “effective” and lack physical meaning, as suggested in a previous work [17] (Frankenberg et al., 2008). In a second step, the conclusions from the laboratory data are tested using ground-based atmospheric solar absorption spectra. The fit residuals obtained confirm the quality of the proposed model and evidence the impact of line mixing on CH₄ atmospheric spectra. The present results also confirm that laboratory and atmospheric spectra can alternatively be accurately modeled neglecting LM and using ad hoc broadening and shifting parameters. Conclusions of this exercise can be drawn from two perspectives. From the point of view of spectroscopy and understanding of processes, accurate line parameters will not be deduced from fits of laboratory measurements unless line-mixing effects are included in the spectral-shape model. In the meantime, and from the point of view of atmospheric retrievals, neglecting LM with suitable effective line parameters is convenient and accurate (within current retrieval uncertainties). Note that this is only true if this approach is not used for total pressures significantly above 1 atm (e.g. Jupiter).     

Experimental He-pressure broadening for the R(10) and P(2) lines in the ν3 band of CO2, and experimental pressure shifts for R(10) measured at several temperatures between 300 K and 100 K

Helium broadening coefficients for the R(10) and the P(2) lines in the ν₃ band of ¹³CO₂ have been measured over a large range of temperature (70 K-300 K). Helium pressure shifts for the R(10) line at several temperatures between 100 K and 300 K have also been determined. These measurements were obtained with a cold Herriott cell, using the collisional cooling technique to reach the lowest temperatures. They provide an extended dataset for the temperature dependence of widths and shifts. This dataset was compared to theoretical He-broadening coefficients combining quantum scattering calculations and the latest potential energy surface for the system He-CO₂ from Korona et al. [T. Korona, R. Moszynski, F. Thibault, J.-M. Maunay, B. Bussery-Honvault, J. Boissoles, P.E.S. Wormer, J. Chem. Phys. 115 (2001) 3074-3084].     

Thermal and optical properties of Tm: Li6Gd(BO3)3 crystal: A potential candidate for 1.83 μm lasers

Single crystal of Tm³⁺: Li₆Gd (BO₃)₃ was grown by the Czochralski method. The heat capacity was measured from 308 to 673 K. The absorption spectra of the crystal in three mutually perpendicular arbitrary directions were measured at room temperature. Based on the Judd-Ofelt theory and the spectra measured in three mutually perpendicular directions, the intensity parameters Ω_t (t=2, 4, 6), the line strengths, the oscillator strengths, the radiative rates, radiative lifetimes and fluorescent branching ratios were calculated. We calculated the emission cross-section by the reciprocity method and also obtained the gain cross-section.     

The ν1, ν2, and ν3 bands of carbonyl chlorofluoride (COFCl) at 5.3, 9.1, and 13.1 μm: position and intensity parameters and their use for atmospheric studies

A list of line positions and, for the first time, of line intensities was generated for the ν₁, ν₂, and ν₃ fundamental bands of the ¹²C¹⁶OF³⁵Cl and ¹²C¹⁶OF³⁷Cl isotopologs of carbonyl chlorofluoride, located at 5.3, 9.1, and 13.1 μm, respectively. In addition, for the most abundant isotopolog (¹²C¹⁶OF³⁵Cl) this linelist includes also the contributions from the first two associated hot bands. The parameters included in this database were generated by combining the results of previous experimental analyses and ab initio calculations [Perrin A, Flaud JM, Bürger H, Pawelke G, Sander S, Willner H. First high resolution analysis of the six fundamental bands ν₁, ν₂, ν₃, ν₄, ν₅ and ν₆ of COF³⁵Cl in the 340 to 2000 cm⁻¹ region. J Mol Spectrosc 2001;209:122-232; Demaison J, Perrin A, Bürger H. Ab initio anharmonic force field and equilibrium structure of carbonyl chlorofluoride. J Mol Spectrosc 2003;221:47-56]. For the purpose of the present work, a partial re-investigation of the ν₁ of COF³⁵Cl was performed, together with the first identification of the ν₂ band of COF³⁷Cl.These parameters were generated in order to improve the quality of remote sensing of the atmosphere in the mid-IR. Analyses of atmospheric solar occultation spectra measured by the JPL MkIV interferometer show that the new linelist not only improves the quality of retrievals of COFCl, but also of several other gases whose absorptions overlap those of COFCl.     

Search for charged Higgs bosons in ee collisions at = 181–184 GeV

Data collected at centre-of-mass energies of 181–184 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 56.9 pb⁻¹, are analysed in a search for pair-produced charged Higgs bosons H^±. Three analyses are employed to select the , / and final states. No evidence for a signal is found. Mass limits are set as a function of the branching fraction B(H⁺→τ⁺ν_τ). Under the assumption that the decay modes considered cover the totality of the possible final states, charged Higgs bosons with masses below 59 GeV/c² are excluded at 95% C.L. independently of B(H⁺→τ⁺ν_τ).     

C( ,pn) photon asymmetry for Eγ=180–340 MeV

The photon asymmetry (Σ) of the ¹²C( ,pn) reaction has been measured using linearly polarised tagged photons at the Mainz microtron MAMI for E_γ=180–340 MeV. The data have been analysed in separate missing energy (E_m) regions corresponding to the ejection of nucleons from (1p)² and (1p)(1s) shells. The measured Σ values for both E_m regions are smaller in magnitude than corresponding ²H data, but the (1p)² results have a similar E_γ dependence. Calculations of direct two-nucleon emission overestimate the magnitude of Σ at all photon energies.