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1.
A quantum cascade laser (QCL)-based absorption sensor for the simultaneous dual-species monitoring of CH4 and N2O was developed using a novel compact multipass gas cell (MGC). This sensor uses a thermoelectrically cooled, continuous wave, distributed feedback QCL operating at ~7.8 µm. The QCL wavelength was scanned over two neighboring CH4 (1275.04 cm?1) and N2O (1274.61 cm?1) lines at a 1 Hz repetition rate. Wavelength modulation spectroscopy (f = 10 kHz) with second harmonic (2f) detection was performed to enhance the signal-to-noise ratio. An ultra-compact MGC (16.9 cm long and a 225 ml sampling volume) was utilized to achieve an effective optical path length of 57.6 m. With such a sensor configuration, a detection limit of 5.9 ppb for CH4 and 2.6 ppb for N2O was achieved, respectively, at 1-s averaging time. 相似文献
2.
L. Gasnot P. Desgroux J.F. Pauwels L.R. Sochet 《Applied physics. B, Lasers and optics》1997,65(4-5):639-646
3 photodissociation is shown to be an important photolytic source of H atoms in the reaction zone of the methane flames. At
226 nm, an efficient energy transfer between O(3P) and N2 is established from the observation of O-resonant emissions from the second positive system of N2. The subsequent rate of O(3P) depletion appears to be essentially “controlled” by the O(3P) concentration and is probably only minimally temperature dependent. Finally quenching rate coefficients for O(3P) by water and nitrogen are deduced from quenching rates measurements performed in CH4/O2/N2 and CH4/O2/Ar flames.
Received: 7 November 1996/Revised version: 28 January 1997 相似文献
3.
D. T. Khoa 《The European physical journal. Special topics》2007,150(1):31-34
DWBA analysis of the inelastic 30-40S(p,p') and
18-22O(p,p') scattering data measured in the inverse kinematics has been
performed to determine the isoscalar (δ0) and isovector (δ1)
deformation lengths of the 2+1 excitations in the Sulfur and Oxygen isotopes
using a compact folding approach. A systematic N-dependence of δ0 and
δ1 has been established which shows a link between δ1 and the
neutron-shell closure. Strong isovector deformations were found in several
cases, e.g., the 2+1 state in 20O where δ1 is nearly three
times larger than δ0. These results confirm the relation
δ1>δ0 anticipated from the core polarization by the valence
neutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell
closure at N=14 or 16 has been discussed based on the folding model analysis
of the inelastic 22O+p scattering data at 46.6 MeV/u measured recently at
GANIL. 相似文献
4.
A. Grossel V. Zéninari B. Parvitte L. Joly D. Courtois 《Applied physics. B, Lasers and optics》2007,88(3):483-492
Room temperature (RT) quantum cascade lasers (QCL) are now available even in continuous wave (cw) mode, which is very promising
for in situ gas detectors. Ambient air monitoring requires high sensitivity with robust and simple apparatus. For that purpose,
a compact photoacoustic setup was combined with two cw QCLs to measure ambient methane and nitrous oxide in the 8 μm range.
The first laser had already been used to calibrate the sensitivity of the photoacoustic cell and a detection limit of 3 ppb
of CH4 with a 1s integration time per point was demonstrated. In situ monitoring with this laser was difficult because of liquid
nitrogen cooling. The second laser is a new RT cw QCL with lower power, which enabled one to reach a detection limit of 34 ppb
of methane in flow. The loss in sensitivity is mainly due to the weaker power as photoacoustic signal is proportional to light
power. The calibration for methane detection leads to an estimated detection limit of 14 ppb for N2O flux measurements. Various ways of modulation have been tested. The possibility to monitor ambient air CH4 and N2O at ground level with this PA spectrometer was demonstrated in flux with these QCLs.
PACS 07.88; 92.60.Sz 相似文献
5.
Optical feedback cavity-enhanced absorption spectroscopy (OF CEAS) has been demonstrated with a thermoelectrically cooled continuous wave distributed feedback quantum cascade laser (QCL) operating at wavelengths around 7.84 μm. The QCL is coupled to an optical cavity which creates an absorption pathlength greater than 1000 m. The experimental design allows optical feedback of infra-red light, resonant within the cavity, to the QCL, which initiates self-locking at each TEM00 cavity mode frequency excited. The QCL linewidth is narrowed to below the mode linewidth, greatly increasing the efficiency of injection of light into the cavity. At the frequency of each longitudinal cavity mode, the absorption coefficient of an intracavity sample is obtained from the transmission at the mode maximum, measured with a thermoelectrically cooled detector: spectral line profiles of CH4 and N2O in ambient air were recorded simultaneously and with a resolution of 0.01386 cm?1. A minimum detectable absorption coefficient of 5.5×10?8 cm?1 was demonstrated after an averaging time of 1 s for this completely thermoelectrically cooled system. The bandwidth-normalised limit for a single cavity mode is 5.6×10?9 cm?1?Hz?1/2 (1σ). 相似文献
6.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
7.
G. Neyens P. Himpe D. L. Balabanski P. Morel L. Perrot M. De Rydt I. Stefan C. Stodel J. C. Thomas N. Vermeulen D. T. Yordanov 《The European physical journal. Special topics》2007,150(1):149-153
This paper reviews recent results from electromagnetic
moment measurements on isotopes in the island of inversion around
N=20. The obtained moments on neutron rich Na, Mg, Al and Si
isotopes allow to draw conclusions on the amount of intruder
components in their ground state wave function, demonstrating a
gradual transition from the normal sd-shell region into the
island of inversion, starting at N=18 for Na, N=19 for Mg and N=20
for Al isotopes. A measurement of the ground state g factor of
35Si (N=21), using a polarized fragment beam at GANIL, is
discussed in more detail. The magnetic moment μ(35Si, Iπ= 7/2-) = (-)1.638(4) μN is consistent with a normal ground
state structure, dominated by a νf7/2 neutron. 相似文献
8.
K. Jessen M. Bergström P. von Brentano A. Dewald B. Herskind H. Meise C. Schumacher G. Sletten O. Stuck D. Weißhaar I. Wiedenhöver J. Wrzesinski 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):113-114
An in-beam experiment with the reaction 122Sn(27Al,4np) at 127 MeV was performed at the Nordball multi-detector array in Roskilde. It provided evidence for a new high-spin
isomer in 144Sm. This isomer with T
1/2= (2.6 ± 0.5) ns at an excitation energy E
x= 9232 keV seems to belong to a family of isomers of similar configuration in neighbouring N= 82 nuclei.
Received: 16 November 1997 相似文献
9.
H. Kettunen T. Enqvist M. Leino K. Eskola P.T. Greenlees K. Helariutta P. Jones R. Julin S. Juutinen H. Kankaanpää H. Koivisto P. Kuusiniemi M. Muikku P. Nieminen P. Rahkila J. Uusitalo 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):457-467
The low-energy nuclear structure and decay properties of the neutron-deficient isotopes 195At and 191Bi have been studied. 195At was produced in the reaction 142Nd(56Fe,p2n)195At and 191Bi as the daughter activity of 195At. The activities were implanted in a position-sensitive silicon detector after being separated from the primary beam by
a gas-filled recoil separator. The 1/2+ intruder state was determined to be the ground state in 195At with an alpha-decay energy of E
α = 6953(3) keV and a half-life T
1/2 = 328(20) ms. Another state with an alpha-decay energy E
α = 7075(4) keV and a half-life T
1/2 = 147(5) ms was found to decay to a 148.7(5) keV excited state in 191Bi for which a spin and parity of 7/2- were deduced. Consequently, the same 7/2- character was assigned to the initial state at 32(7) keV in 195At on the basis of unhindered alpha-decay. The 9/2- state, being the ground state in heavier odd-mass astatine isotopes, was not observed.
Received: 16 September 2002 / Accepted: 19 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: heikki.kettunen@phys.jyu.fi
RID="b"
ID="b"Present address: Laboratory of Radiochemistry, P.O. Box 55, FIN-00014, University of Helsinki, Finland.
RID="c"
ID="c"Present address: Radiation and Nuclear Safety Authority, P.O. Box 14, FIN-00881 Helsinki, Finland.
Communicated by W. Henning 相似文献
10.
A. Tumino M. Lattuada S. Romano C. Spitaleri D. Vinciguerra Z. Basrak O.Yu. Goryunov V.V. Ostashko S. Szilner P. Figuera D. Lo Presti C. Petta N. Randazzo S. Reito G.V. Russo S. Tudisco 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):327-334
High-spin states of 24Mg produced in the 16O + 12C interaction and decaying into the 16Og.s. + 8Beg.s. channel have been observed in the excitation region between 35 and 52 MeV. Spins have been assigned on the basis of the analysis
of the measured angular correlations. Some of these states with positive parity correspond to the known resonances of the
12C( 12C, 8Beg.s.) 16O reaction belonging to the 16O-2α rotational band of 24Mg. Moreover other resonances show up at higher excitation energy with an energy-spin relationship again suggesting a 16O-2α cluster structure for the associated configuration.
Received: 6 July 2001 / Accepted: 16 October 2001 相似文献
11.
W. A. Brand 《Isotopes in environmental and health studies》2013,49(3-4):277-284
Abstract For the high precision isotope analysis of atmospheric trace gases a computer controlled concentration interface has been developed. From small air samples it collects either N2O or CO2 derived from CH4 at their respective concentrations (0.3 ppm for N2O, 1.7 ppm for CH4) into a small diameter cold trap (?196°C) and interfaces via GC and open split to an isotope ratio mass spectrometer (Finnigan MAT 252) for on-line isotope evaluation. External reproducibilities for repeated measurements of 100 ml air samples from the same source of < 0.2° (δ-notation) have been achieved for 13C/12C from CH4 and for 15N/14N and 18O/16O from N2O. The precision is adequate to monitor the isotopic changes in these gases during a day's course. 相似文献
12.
R. Kalpakchieva H.G. Bohlen W. von Oertzen B. Gebauer M. von Lucke-Petsch T.N. Massey A.N. Ostrowski Th. Stolla M. Wilpert Th. Wilpert 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):451-461
New information has been obtained on excited states of the neutron-rich boron isotopes 14B, 15B and 16B, using the reactions 12C(14C,12N)14B, 13C(14C,12N)15B and 14C(14C,12N)16B at about 24 MeV/A. The mass excess of 16B has been measured for the first time, it is 37.08(6) MeV. This means that 16B is unbound by only 0.04(6) MeV. Furthermore, the nucleus 13B has been investigated with the four reactions 16O(14C,17F), 12C(14C,13N), 12C(13C,12N) and 12C(15N,14O). Choosing different target-projectile combinations, it was possible to populate states with different selectivity. New
states are observed in 13B at excitation energies above the threshold for two-neutron decay.
Received: 27 December 1999 / Revised version: 11 February 2000 相似文献
13.
Oelschlaeger C Buhler E Waton G Candau SJ 《The European physical journal. E, Soft matter》2003,11(1):7-20
The mixed micellization between the cationic gemini surfactant [ C12H25( CH3)2N+( C2H4) N+( CH3)2 C12H25•2Br-] and the cationic cetyltrimethylammonium bromide (CTAB) in 150 mM KBr solutions has been investigated. The variation of the
cmc of the mixtures, measured by surface tension experiments, with composition revealed synergism in micelle formation. T-Jump
and light scattering experiments performed in the vicinity of the crossover volume fraction showed the existence of two micellar
populations, possibly linear and toroidal micelles. Rheological and dynamic light scattering experiments allowed to fully
characterize the linear viscoelasticity of the mixtures. These measurements revealed synergistic gains in viscoelastic properties
with a maximum of the stress-relaxation time around the equimolar composition. These effects are ascribed to a progressive
intermicellar crosslinking resulting from a continuous increase of the end-cap energy with the 12-2-12 content in the mixture.
Received: 18 November 2002 / Accepted: 8 April 2003 / Published online: 27 May 2003
RID="a"
ID="a"e-mail: candau@fresnel.u-strasbg.fr 相似文献
14.
The isospin dependence of shell closure phenomena is studied for light neutron-rich nuclei within a microscopic self-consistent
approach using the Gogny force. Introducing configuration mixing, 32Mg is found to be dynamically deformed, although the N = 20 spherical shell closure persists at the mean-field level for all N = 20 isotones. In contrast, the N = 28 spherical shell closure is found to disappear for N - Z≥ 10 whereas deformed shell closures are preserved and lead to shape coexistence in 44
S. Configuration mixing shows that the ground state of this nucleus is triaxially deformed. The first 2+ excitation energy Ex = 1.46 MeV and the reduced transition probability B(E2;0+
gs→ 2+
1)= 420 e
2
fm
4 obtained with our approach are in good agreement with experimental data.
Received: 26 July 2000 / Accepted: 30 August 2000 相似文献
15.
T. Kautzsch W.B. Walters M. Hannawald K.-L. Kratz V.I. Mishin V.N. Fedoseyev W. Böhmer Y. Jading P. Van Duppen B. Pfeiffer A. Wöhr P. Möller I. Klöckl V. Sebastian U. Köster M. Koizumi J. Lettry H.L. Ravn the ISOLDE Collaboration 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):201-206
A chemically selective laser ion source has been used in a β-decay study of heavy Ag isotopes into even-even Cd nuclides.
Gamma-spectroscopic techniques in time-resolving event-by-event and multiscaling modes have permitted the identification of
the first 2+ and 4+ levels in 126Cd78, 128Cd80, and tentatively the 2+ state in 130Cd82. From a comparison of these new states in 48Cd with the E(2+) and E(4+)/E(2+) level systematics of 46Pd and 52Te isotopes and several recent model predictions, possible evidence for a weakening of the spherical N = 82 neutron-shell below double-magic 132Sn is obtained.
Received: 13 July 2000 / Accepted: 12 October 2000 相似文献
16.
A. Bielski D. Lisak R.S. Trawiński J. Szudy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):217-222
Using a laser-induced fluorescence method a detailed analysis of profiles of the 114Cd 326.1 nm line perturbed by N2 and CH4 was performed which revealed deviations from the ordinary Voigt profile. These deviations are shown to be consistent with
fits of experimental profiles to an asymmetric Voigt profile. Coefficients of the pressure broadening, shift and collision-time
asymmetry are determined and compared with those calculated for van der Waals interaction potential.
Received 29 November 2001 / Received in final form 12 July 2002 Published online 4 February 2003 相似文献
17.
M.G. Donato G. Faggio M. Marinelli G. Messina E. Milani A. Paoletti S. Santangelo A. Tucciarone G. Verona Rinati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):133-139
High quality synthetic diamonds were grown on single-crystal silicon by microwave plasma enhanced chemical vapour deposition
(CVD). A careful optimisation of both the experimental setup and the growth parameters was necessary before that the achievement
of the best results was made possible. The films were deposited using a CH4-H2 gas mixture at methane concentrations variable in the range 0.6-2.2%, while the substrate temperature was fixed at 750 °C. Raman spectroscopy and photoluminescence (PL) were utilised to monitor the quality of the deposited films and to study
the spatial distribution of defects, respectively. Micro-Raman analysis shows that linewidths of the diamond peak lower than
2.4 cm-1 can be easily measured at the growth surface, indicating that the crystalline quality of individual grains is comparable
to that of the best natural diamonds. The excellent phase purity of the diamond microcrystals at the growth surface is witnessed
by the complete absence of any non-diamond carbon feature and by a very weak luminescence background in the 1.6-2.4 eV spectral
range. A worsening of the quality of the diamond particles is found moving from the growth surface towards the film-substrate
interface. A photoluminescence feature at about 1.68 eV, commonly associated to Si impurities, is distinctly observed as the
exciting laser beam is focused close to the interface. A progressive degradation of the global quality of the films is found
with increasing methane concentration in the gas mixture, as witnessed by an increased PL background in the films grown at
higher methane concentrations.
Received 24 November 2000 相似文献
18.
E. Costanzo A. Cunsolo A. Foti O.Yu. Goryunov M. Lattuada V.V. Ostashko L. Putaggio S. Romano C. Spitaleri A. Tumino D. Vinciguerra Yu Xian 《The European Physical Journal A - Hadrons and Nuclei》1999,5(1):69-75
8Begs coincidences with 12C, 8Begs and α-particles produced in the 12C +12C interaction at 65 MeV have been measured in a wide in-plane angular range. The 3 −8Begs final state is found to be produced, even if poor statistics prevent any identification of the 16O states involved in the first stage of the process. The 8Begs−α and 8Begs−12C coincidence yields are found to be due to 12C and 16O excited states, decaying into the 8Begs+α and 12C +α systems, respectively.
Received: 15 June 1998 / Revised version: 4 December 1998 相似文献
19.
S. Leenhardt O. Sorlin M.G. Porquet F. Azaiez J.C. Angélique M. Belleguic C. Borcea C. Bourgeois J.M. Daugas C. Donzaud I. Deloncle J. Duprat A. Gillibert S. Grévy D. Guillemaud-Mueller J. Kiener M. Lewitowicz S.M. Lukyanov F. Marie N.A. Orr Yu.-E. Penionzhkevich F. de Oliveira Santos F. Pougheon M.G. Saint-Laurent W. Shuying Yu. Sobolev J.S. Winfield 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):1-5
The reduced transition probability B(E2: 01
+→ 2+) of 72Zn has been measured for the first time by Coulomb excitation at intermediate energy. The result B(E2: 01
+→ 2+) = 1740±210 e2fm4, corresponds to the deformation parameter β2 of 0.23, in close agreement with expectations derived from the neighboring nucleus 73Zn. A discussion of the evolution of the N = 40 sub-shell closure as a function of Z is presented.
Received: 19 December 2001 / Accepted: 14 March 2002 相似文献
20.
Y.P. Gangrsky D.V. Karaivanov K.P. Marinova B.N. Markov L.M. Melnikova G.V. Mishinsky S.G. Zemlyanoi V.I. Zhemenik 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):313-318
The hyperfine structure of the D2 optical line in 22Na and 23Na has been investigated using high resolution laser spectroscopy of a well-collimated atomic beam. The hyperfine splitting
constants A and B for the excited 3p 2P3/2 level for both investigated sodium isotopes have been obtained. They are as follows: A(22) = 7.31(4) MHz, B(22) = 4.71(28)
MHz, A(23) = 18.572(24) MHz, B(23) = 2.723(55) MHz. With this data, using the high precision MCHF calculations for the electric
field gradient at the nucleus, the electric quadrupole moment of 22Na has been deduced: Qs(22) =+0.185(11) b. The sign of Qs(22), determined for the first time, indicates a prolate nuclear deformation. A precise value of the isotope shift 22,23Na in the D2 line has also been obtained.
Received: 26 February 1998 / Revised version: 25 June 1998 相似文献