Diode-laser absorption measurements of CO2, H2O, N2O, and NH3 near 2.0 μm

2 , H₂O, N₂O, and NH₃ concentrations in various flowfields using absorption spectroscopy and extractive sampling techniques. An external-cavity diode laser with a tuning range of 1.953–2.057 μm was used to record absorption lineshapes from measured transitions in the CO₂ 4ν₂ ⁰+ν₃, ν₁+2ν₂ ⁰+ν₃, and 2ν₁+ν₃ bands, H₂O ν₂+ν₃and ν₁+ν₂ bands, N₂O 2ν₁+4ν₂ ⁰, ν₂ ¹+2ν₃, 3ν₁+2ν₂ ⁰, and 4ν₁ bands, and NH₃ν₁+ν₄ and ν₃+ν₄ bands. Measured CO₂, H₂O, and N₂O survey spectra were compared to calculations to verify the HITRAN96 database and used to determine optimum transitions for species detection. Individual lineshape measurements were used to determine fundamental spectroscopic parameters including the line strength, line-center frequency, and self-broadening coefficient of the probed transition. The results represent the first measurements of CO₂, H₂O, N₂O, and NH₃ absorption near 2.0 μm using room-temperature near-IR diode lasers. Received: 12 March 1998/Revised version: 7 May 1998     

Search for D+→φl+ν and measurement of the branching fraction for D+→φπ+

Using a data sample of integrated luminosity of about 33 pb^-1 collected around 3.773 GeV with the BESII detector at the BEPC collider, the semileptonic decays D⁺→φe⁺ν_e, D⁺→φμ⁺ν_μ and the hadronic decay D⁺→φπ⁺ are studied. The upper limits of the branching fractions are set to be BF(D⁺→φe⁺ν_e)<2.01% and BF(D⁺→φμ⁺ν_μ)<2.04% at the 90% confidence level. The ratio of the branching fractions for D⁺→φπ⁺ relative to D⁺→K^-π⁺π⁺ is measured to be 0.057±0.011±0.003. In addition, the branching fraction for D⁺→φπ⁺ is obtained to be (5.2±1.0±0.4)×10^-3.     

Electron-vibrational energy exchange in collisions of Ar atoms in the 3P2 metastable state with N2(X1S g+ ) molecules

Rate constants for electron-vibrational energy exchange Ar(³ P ₂) + N₂(X ¹Σ _g ⁺, ν = 0) → Ar(¹ S ₀) + N₂(C ³Π _u , ν′), where ν′ = 0, 1, 2, were calculated. Calculations were performed taking into account the presence of a resonance in electron scattering by N₂(X ¹Σ _g ⁺). As a result, the interaction of Ar(³ P ₂) with N₂(X ¹Σ _g ⁺, ν = 0) was characterized by attraction and, in the end, intersection of electron-vibrational potential surfaces correlating with Ar(³ P ₂) + N₂(X ¹Σ _g ⁺, ν = 0) and Ar(¹ S ₀) + N₂(C ³Π _u , ν′) at interparticle distances of 2.5–3.5 ?. Exchange interaction at which electron-vibrational transitions in the region of intersection of electron-vibrational transitions in the region of intersection of electron-vibrational potential surfaces accompanied by spin exchange were induced was calculated by the asymptotic method. The rate constants determined at 300–600 K were on the order of 10⁻¹¹−10⁻¹² cm³/s and weakly increased as the temperature grew. Mainly the C ³Π _u , ν′ = 0 state of the N₂ molecule was populated. The calculation results were in satisfactory agreement with the experimental data obtained at 300 K.     

Line strength and collisional broadening studies of hydrogen sulphide in the 1.58 μm region using diode laser spectroscopy

High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different transitions within the region of the ν ₁+ν ₂+ν ₃ and 2ν ₁+ν ₂ combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H₂S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy (WMS). The set-up sensitivity has been calculated as 1.73×10⁻⁸ cm⁻¹ s^1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated to the intermolecular potentials governing the collision process; the H₂S–H₂S dimer well depth is estimated to be 7.06±0.09 kJ mol⁻¹.     

NaNe potentials from a combined analysis of spectroscopic and scattering data

Experimental differential cross sections for the optical collision process Na(3s)+Ne+hν→Na(3p)+Ne and spectroscopic data for A²Π→X²Σ⁺optical transitions are used to obtain the potential curves for the X²Σ⁺ground and A²Π first excited states of the NaNe molecule and the spin-orbit function g_so(r).     

Measurements of the absolute branching fractions for D→K̄πe+νe, D→K̄*e+νe and determination of Γ(D+→K̄*0e+νe)/Γ(D+→K̄0e+νe)

Using the data of about 33 pb^-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic decays D⁺→K^-π⁺e⁺ν_e, D⁰→K̄⁰π^-e⁺ν_e, D⁺→K̄^*0e⁺ν_e and D⁰→K^*-e⁺ν_e. The absolute branching fractions for the decays are measured to be BF(D⁺→K^-π⁺e⁺ν_e)=(3.50±0.75±0.27)%, BF(D⁰→K̄⁰π^-e⁺ν_e)=(2.61±1.04±0.28)%, BF(D⁺→K̄^*0e⁺ν_e)=(5.06±1.21±0.40)% and BF(D⁰→K^*-e⁺ν_e)=(2.87±1.48±0.39)%. The ratio of the vector to pseudoscalar semileptonic decay rates Γ(D⁺→K̄^*0e⁺ν_e)/Γ(D⁺→K̄⁰e⁺ν_e) is determined to be 0.57±0.17±0.02.     

High-resolution investigation of the weak ν1+3ν21-ν21+ν3 band of CO2 around 2 μm

Fundamental spectroscopical parameters of the weak ν₁+3ν₂ ¹-ν₂ ¹+ν₃ band of CO₂ are reported using a high-resolution, direct-absorption spectrometer, based on a distributed feed-back diode laser emitting at 2 μm. Line intensities and self-broadening coefficients have been measured for the first time with high accuracy, for nine lines of the R branch, from R(44) up to R(59). Comparison with available data has been made, and a generally good agreement has been found. Received: 30 August 1999 / Published online: 24 March 2000     

First results for the measurement of double-electron capture of 106Cd in the experiment TGV II

Present status of the experiment TGV II which is devoted to the measurement of double-beta decay of ¹⁰⁶Cd is given. The low background spectrometer TGV II is installed in the Modane Underground Laboratory and has been running from February 2005 with approx 10 grams of ¹⁰⁶Cd enriched at 75%. After an analysis of 3736 hours of experimental data the new improved half-life limit for 2νEC/EC decay of ¹⁰⁶Cd (0 _g.s. ⁺ → 0 _g.s. ⁺ ) is given as T ₁ ^2/2ν > 4.8 × 10¹⁹ years (90% CL). The search for 2νEC/EC decay of ¹⁰⁶Cd to the excited states of ¹⁰⁶Pd allows to determine the limits of the half-lives T ₁ ^2/2ν (0 _g.s. ⁺ → 2 ₁ ⁺ ) > 3.9 × 10¹⁹ years (90% CL) and T ₁ ^2/2ν (0 _g.s. ⁺ → 0 ₁ ⁺ ) > 5.8 × 10¹⁹ years (90% CL). Presented by I. Štekl at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

ECTDL study of N 2 - and O 2 -pressure broadening of a series of ammonia lines in the 1.5 μm (ν 1 +ν 3 ) combination band

Nitrogen and oxygen pressure broadening parameters for seven ^r P(J”,0) transitions of the ν₁+ν₃ overtone band of the main isotope of ammonia with J” varied from 2 to 9 have been measured at room temperature using an external cavity tunable diode laser spectrometer. Air-broadening parameters have also been calculated from the N₂ and O₂ measurements. The results are compared to previous measurements in the ν₁, ν₂, ν₃, ν₄ and ν₁+ν₃ bands and to the parameters for the ν₃ band that are reported in the HITRAN database. PACS 33.70.Jg; 33.70.-W; 33.20.Ea; 42.62.Fi; 42.68.Ca     

Dynamics of low-energy nuclear forces for electromagnetic and weak reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei

A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n + p → D + γ, the photomagnetic disintegration of the deuteron γ + D → n + p and weak reactions of astrophysical interest. These are the solar proton burning p + p → D + e⁺ + ν _e, the pep-process p + e⁻ + p → D + ν _e and the neutrino and antineutrino disintegration of the deuteron caused by charged ν _e + D → e⁻ + p + p, + D → e⁺ + n + n and neutral ν _e() + D → ν _e() + n + p weak currents.     

Search for exotic contributions to atmospheric neutrino oscillations

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν _μ → ν _τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10⁻²⁴ at sin(2ϑ_υ) = 0 and |Δυ| < (2.5–5) × 10⁻²⁶ at sin(2ϑ_υ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle. The text was submitted by the author in English.     

Prospects for the measurement of the structure of the coupling of a Higgs boson to weak gauge bosons in weak boson fusion with the ATLAS detector

The prospects for the measurement of the tensor structure of the vertex between a standard model Higgs boson and two weak gauge bosons using the distribution of the azimuthal angles between the two tagging jets in the weak boson fusion channel are studied in a Monte Carlo analysis using the fast simulation of the ATLAS detector. The decay channels H→τ⁺τ^-→ll+4ν, H→τ⁺τ^-→lh+3ν at m_H=120 GeV and H→W⁺W^-→llνν at m_H=160 GeV are used in the analysis. For a standard model Higgs boson it is found that purely anomalous couplings are expected to be excluded at a confidence level corresponding to 2σ or more at m_H=120 GeV and more than 5σ at m_H=160 GeV from 30 fb^-1 of data. With a value of 1 roughly reproducing the standard model cross section for a purely anomalous coupling, the standard deviation in a measurement of a contribution of a CP even anomalous coupling in addition to the standard model coupling is estimated to be 0.20 at m_H=120 GeV and 0.09 at m_H=160 GeV.     

Structure of low-spin states in the doubly-odd 182Ir nucleus

Low-spin states of ¹⁸²Ir were populated through the β⁺ /EC decay of ¹⁸²Pt . Two strong E2 transitions were observed for the first time: a 25.7keV transition in ¹⁸²Ir and a 34.0keV transition in Re of probable mass A = 178 . Spin and parity, I ^π = 3⁺ , are firmly assigned to the ¹⁸²Ir ground state (g.s.). For the excited states, the parity is established and the spin determined or restricted. These assignments support most of the interpretations of the level structure previously suggested. The systematics for the known 5⁺ → 3⁺ transitions in π h _9/2 ⊗ ν 1/2^-[521] bands is presented. Using a semi-microscopic two-quasiparticle axial-rotor coupling model, particle configurations have been attributed or suggested for most of the coupled states lying at low energy in ¹⁸²Ir .     

Frequency-stabilized cavity ring-down spectrometer for high-sensitivity measurements of water vapor concentration

We present a portable spectrometer that uses the frequency-stabilized cavity ring-down spectroscopy technique capable of high-precision measurements of trace water vapor concentration. Measuring one of the strongest rovibrational transitions in the ν₁+ν₃ water vapor combination band near ˜ν=7181.156 cm^-1, we compare spectroscopic and thermodynamic determinations of trace water vapor in N₂, and find systematic differences attributable to water vapor background effects and/or uncertainties in line intensities. We also compare the frequency-stabilized ring-down method with other cavity ring-down approaches that are based on unstabilized probe lasers and unstabilized ring-down cavities. We show that for the determination of water vapor concentration, the frequency-stabilized cavity ring-down method has the minimum measurement uncertainty of these techniques. The minimum noise-equivalent absorption coefficient of the spectrometer was 1.2×10^-10 cm^-1 Hz^-1/2, which further corresponds to a minimum detectable water vapor mole fraction equal to 0.7×10^-9 for an absorption spectrum of 10 minutes duration. PACS 33.20.-t; 33.70.Jg; 33.70.Fd; 42.62.Fi     

Thermal grating and broadband degenerate four-wave mixing spectroscopy of OH in high-pressure flames

2 ∑–X²Π(0,0) band of OH has been studied in premixed methane/air flames using a cw Ar⁺ laser probe. Measurements of flame temperature and pressure were derived from fits of theoretical simulations to the observed time variation of signals over a pressure range of 10 to 40 bar and for different stoichiometry that were in agreement with independent measurements using N₂ CARS and predictions of a one-dimensional flame calculation. Broadband DFWM spectra in the same band of OH were observed up to a pressure of 9 bar, above which signals were obtained only from scattering from thermal gratings. Received: 10 November 1997/Revised version: 28 May 1998     

Carbon dioxide and ammonia detection using 2 μm diode laser based quartz-enhanced photoacoustic spectroscopy

Quartz-enhanced photoacoustic spectroscopy was employed for trace gas concentration measurements of CO₂ and NH₃ using a continuous wave thermoelectrically cooled, distributed feedback diode laser operating at 2 μm. A normalized noise equivalent absorption coefficient, NNEA(1σ)=1.4×10^-8 cm^-1W/ was obtained for CO₂ using the R18 line of the 2ν₁+ν₃ band at 4991.26 cm^-1. This corresponds to minimum detection limit (1σ) of 18 parts per million (ppm) for a 1 s lock-in time constant. The influence of the H₂O presence in the sample gas mixture on the CO₂ sensor performance was investigated. Ammonia detection was performed using the ^P P ₆(6)_S line of the ν₃+ν₄ band at 4986.99 cm^-1. A detection limit (1σ) of 3 ppm for NH₃ concentration with a 1 s lock-in time constant was achieved. This results in a normalized noise equivalent absorption of NNEA(1σ)=8.9×10^-9 cm^-1W/. PACS 82.80.Kq; 46.62.Fi; 42.55.Px     

Gas temperature measurements using widely tunable long-wavelength VCSEL

A method for gas temperature measurements with a widely tunable laser diode is presented. The method involves rapidly switching the laser frequency between two distantly spaced absorption lines chosen for optical thermometry. Direct absorption spectroscopy using a single-mode VCSEL was employed to probe the R10 and R22 lines of the 2ν₁+2ν₂ ⁰+ν₃ combination band of CO₂ near 6355.9 and 6363.7 cm^-1 sequentially. A specially designed 0.5-m cryogenic gas cell was filled with 10 mbar CO₂ at room temperature and cooled to 150 K with liquid N₂. The VCSEL was modulated with a 10-kHz ramp superimposed on a 1-kHz square waveform to scan two 0.04 cm^-1 intervals sequentially. The gas temperatures obtained with the VCSEL in the 150–300 K range are in a good agreement with those derived from gas pressure ratios. The maximum relative error of temperature measurements using the VCSEL was ± 3%. A compact VCSEL-based sensor can be developed for gas temperature and concentration measurements in the Martian atmosphere. The method proposed can be used for many applications including in situ monitoring of combustion processes. PACS 42.62.Fi; 42.55.Px; 39.30.+w     

Detecting an invisible Higgs boson at Fermilab Tevatron and CERN LHC

In this paper, we study the observability of an invisible Higgs boson at Fermilab Tevatron and CERN LHC through the production channel qq̄→ZH→ℓ⁺ℓ^-+P/_T, where/P_T is reconstructed from the ℓ⁺ℓ^- with ℓ=e or μ. A new strategy is proposed to eliminate the largest irreducible background, namely qq̄→Z(→ℓ⁺ℓ^-)Z(→νν̄). This strategy utilizes the precise measurements of qq̄→Z(→ℓ⁺ℓ^-)Z(→ℓ⁺ℓ^-). For m_H=120 GeV and with luminosity 30 fb^-1 at Tevatron, a 5σ observation of the invisible Higgs boson is possible. For m_H=114∼140 GeV with only 10 fb^-1 luminosity at LHC, a discovery signal over 5σ can be achieved. PACS 14.80.Cp     

Calculation of radiative transition probabilities and radiative recombination rate coefficients for H2, OH, H 2+ and OH+ molecules

A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B → X) and Werner (C → X) band systems of H₂ and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between H₂⁺ (X) and H₂(X), and between OH⁺(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated as a function of temperature in the range 1500–15 000 K.     

Resonant photoacoustic simultaneous detection of methane and ethylene by means. of a 1.63-μm diode laser

A compact multi-component trace-gas detector based on the resonant photoacoustic technique and a NIR external cavity diode laser has been developed. It has been characterized using a mixture of ethylene and methane diluted in ambient air. A spectroscopic investigation of combination bands and overtones between 5900 and 6250 cm^-1, obtained with an IR pulsed laser photoacoustic spectrometer, allowed us to find a wavelength region where the 2ν₃ overtone of CH₄ and the ν₅+ν₉ combination band of C₂H₄ show uncongested rotational lines. Using a single-mode scan of the diode laser in this region, around 6150 cm^-1, the sensitivity for the simultaneous detection of ethylene and methane is 8 ppm/mW and 40 ppm/mW respectively. Factors affecting the sensitivity and selectivity of the detection system and possible improvements suitable to reach the sub-ppm detection limit are discussed. Received: 1 August 2001 / Revised version: 28 November 2001 / Published online: 7 February 2002 An erratum to this article is available at .