共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Hayashi T. Suzuki T. Ichimura K. Tsukiyama 《Applied physics. B, Lasers and optics》1997,65(4-5):555-561
2 Σ+,H′2Π(v′=0)←X2Π(v′′=0) two-photon transition of NO, both near-infrared and vacuum ultraviolet radiation were emitted along the laser propagation
direction. The analyses of emission and excitation spectra revealed that the parametric four-wave mixing (PFWM) process coexisted
with amplified spontaneous emission. Polarization properties of the IR radiation are found to be dependent on the rotational
levels. Pressure and laser power behaviors of the generated waves were reported. The mechanism of PFWM was discussed in terms
of selection rules of the relevant ro-vibronic transitions.
Received: 19 September 1996/Revised version: 27 January 1997 相似文献
2.
The use of rovibrationally excited NO photofragments as trace nitrocompounds indicators 总被引:6,自引:0,他引:6
A one-color laser performs photolysis of nitrocompounds and laser-induced fluorescence to monitor the generated NO photofragments
and to sensitively detect vapor trace amounts of nitrocompounds. The NO is monitored via excitation and emission through A2Σ+(v′=0)?X2Π(v′′=2-0) and A2Σ+(v′=0)?X2Π(v′′=0,1) transitions, respectively. It is found that NO photofragments populate the vibrationless ground state and also the first
two vibrationally excited states. The analytical performance of the method is demonstrated on 2,4 dinitrotoluene (DNT) via
excitation through A2Σ+(v′=0)?X2Π(v′′=2). The achieved limits of detection are 3.7 and 2.7 parts per billion (ppb) by weight of gaseous DNT in 100 and 500 Torr
of air, for 30 s integration time. The application of this scheme for trace nitrocompound detection has the advantage that
no background of ambient ground-state NO interferes and that the fluorescence is collected at shorter wavelengths than the
exciting radiation, precluding background fluorescence.
Received: 18 August 1999 / Revised version: 22 November 1999 / Published online: 8 March 2000 相似文献
3.
L. Pereira A. Morozov M. M. Fraga T. Heindl R. Krücken J. Wieser A. Ulrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(3):325-334
The temperature dependences of the quenching rate constants of the states
N2 (${\rm C} \ {^{3}{
\rm \Pi }_{u}}${\rm C} \ {^{3}{
\rm \Pi }_{u}} v′=0,1) by N2 (X) and of the state
N2 (${\rm C} \ {^{3}{
\rm \Pi }_{u}} \ v^{\prime}=0${\rm C} \ {^{3}{
\rm \Pi }_{u}} \ v^{\prime}=0) by O2 (X) are studied.
Time-resolved light emission from the gas was analyzed in the temperature
range from 300 K to 210 K keeping the gas at constant density. In case of
quenching by N2 (X), the quenching rate constant for the vibrational
level v′= 0 increases by (13 ±3)% with gas cooling whereas the
quenching rate constant for v′= 1 decreases by (5.0 ±2.5)% in this
temperature range. For quenching by O2 (X), the quenching rate constant
decreases by (3 ±2)% with gas cooling. The temperature variation of
the N2 (C 3Πu v′=0) emission intensity for pure nitrogen
and dry air are calculated using the obtained quenching rate constants and
is compared with the experimental data available in the literature. 相似文献
4.
M. Versluis N. Georgiev L. Martinsson M. Aldén S. Kröll 《Applied physics. B, Lasers and optics》1997,65(3):411-417
1 (6) rotational line in the A2Σ+(v′=0)←X2Π(v′′=0) band of OH at 309 nm. The requirements for obtaining a good signal-to-noise ratio for the technique are discussed and
the possibilities of single-shot measurements are investigated.
Received: 31 October 1996/Revised version: 3 December 1996 相似文献
5.
J. J. Camacho M. Santos L. Díaz L. J. Juan J. M. L. Poyato 《Applied Physics A: Materials Science & Processing》2010,99(1):159-175
A spectroscopic study of ambient air plasma, initially at room temperature and pressures ranging from 32 to 101 kPa, produced
by high-power transverse excitation atmospheric (TEA) CO2 laser (λ=9.621 and 10.591 μm; τ
FWHM≈64 ns; power densities ranging from 0.29 to 6.31 GW cm−2) has been carried out in an attempt to clarify the processes involved in laser-induced breakdown (LIB) air plasma. The strong
emission observed in the plasma region is mainly due to electronic relaxation of excited N, O and ionic fragments N+. The medium-weak emission is due to excited species O+, N2+, O2+, C, C+, C2+, H, Ar and molecular band systems of N
2+(_{2}^{+}(
B
2\varSigma u+^{2}\varSigma _{\mathrm{u}}^{+}
–X
2\varSigma g+)^{2}\varSigma _{\mathrm{g}}^{+})
, N2(C3
Π
u–B3
Π
g), N
2+(_{2}^{+}(
D2
Π
g–A2
Π
u) and OH(A2
Σ
+–X2
Π). Excitation temperatures of 23400±700 K and 26600±1400 K were estimated by means of N+ and O+ ionic lines, respectively. Electron number densities of the order of (0.5–2.4)×1017 cm−3 and (0.6–7.5)×1017 cm−3 were deduced from the Stark broadening of several ionic N+ and O+ lines, respectively. Estimates of vibrational and rotational temperatures of N
2+_{2}^{+}
electronically excited species are reported. The characteristics of the spectral emission intensities from different species
have been investigated as functions of the air pressure and laser irradiance. Optical breakdown threshold intensities in air
at 10.591 μm have been measured. 相似文献
6.
I. Klincare M. Tamanis R. Ferber A. Zaitsevskii E. A. Pazyuk A. V. Stolyarov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):373-378
Radiative lifetimes for 2≤v′≤44 rovibronic C1Σ+ state levels of NaRb and quenching collision cross-sections with Rb atoms have been directly measured in a thermal cell by
detecting time resolved laser induced fluorescence after pulsed excitation. Many body multipartitioning theory was applied
to calculate C1Σ+-X1Σ+ and C1Σ+-A1Σ+ transition dipole moments. The relevant
ab initio matrix elements were converted to the C1Σ+ state radiative lifetimes. The strong spin-orbit A1Σ+∼ b3Π coupling effect on the total C → A transition probabilities and lifetimes of the C1Σ+ state is discussed. The measured radiative lifetimes show a decrease from 61 to 34 ns as the v′ values increase, the results being in good agreement with calculations. The averaged collisional quenching cross-section
value σ=(3±1)×10-14 cm2 was determined for NaRb (C1Σ+) + Rb collisions from the Stern-Volmer plots. 相似文献
7.
J. Luque R.J.H. Klein-Douwel J.B. Jeffries D.R. Crosley 《Applied physics. B, Lasers and optics》2000,71(1):85-94
Excitation and dispersed laser-induced fluorescence spectra of CH B 2Σ-v′=0,1 in methane flames are analyzed using rotational relaxation models to investigate their applicability for flame diagnostics.
The existence of non-predissociative and highly predissociative rotational levels in the same vibrational state provides a
unique scenario to test the effects of rotational relaxation in laser-induced fluorescence measurements. Using a statistical
power gap law for rotational relaxation modeling, we find that the levels with collision-free lifetimes as short as 100 ps
have apparent fluorescence yields larger than expected because of the extent of rotational relaxation at atmospheric pressure.
Also, vibrational (v′=1 to v′=0) and electronic energy transfer (B 2Σ-v′=1 to A 2Δ) are competitive, and together are half the value for the total collisional removal rate from CH B 2Σ-v′=0. The measured electronic energy transfer branching ratio into A (v′=0-3) depends on the initial rotational level pumped, and energy gap considerations can be used to explain these propensities.
The combination of measurements and model calculations finds the excitation of the CH B 2Σ- v′=1,N′=8 level a good candidate for laser-induced fluorescence quantitative measurements in flames at atmospheric pressure.
Received: 24 September 1999 / Published online: 7 June 2000 相似文献
8.
R.B. López-Martens T.W. Schmidt G. Roberts 《Applied physics. B, Lasers and optics》2002,74(6):577-581
The cycle-averaged ac Stark effect associated with the [
A
]2Σ+v′=2?[
X
]2Π1/2v′=0 two-photon absorption of NO at intensities between 7.7 and 15.2 TW cm-2 has been characterized in real time through a synergic combination of bichromatic laser experiments and quantum-dynamics
calculations. Measurements of the fluorescence emitted by the Rydberg [
A
]2Σ+v′=2 level as a function of time between Stark and probe components of a bichromatic field exhibit a characteristic evolution
in temporal peak structure with Stark-field intensity, which is interpreted in terms of a time-dependent Floquet analysis
of the laser–matter interaction. The experimental observations are consistent with a dynamic Stark shift of Δεs(ω1,ω2)≤0.23 eV of the optical transition at these intensities.
Received: 18 January 2002 / Revised version: 6 March 2002 / Published online: 24 April 2002 相似文献
9.
Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules
Neji Khelifi Riadh Dardouri Omar Marzook Al-Dossary Brahim Oujia 《Journal of Russian Laser Research》2009,30(2):172-186
Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states
of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in 1,3Σ, 1,3Π, and 1,3Δ symmetries are presented. Adiabatic results are also reported for 2Σ, 2Π, and 2Δ electronic states of the molecular ion LiNa+ dissociating into Li (2s, 2p, 3s, and 3p) + Na+ and Li+ + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and Na (1s22s22p6) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and
LiNa+ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between
electronic states of 2Σ and 2Π symmetries is related to the charge transfer process between the two ionic systems Li+Na and LiNa+. 相似文献
10.
Laser-induced breakdown spectrum has been recorded in the region of 380–455 nm using second harmonics of Nd:YAG laser, computer-controlled
TRIAX 320 M monochromator with a reciprocal linear dispersion 2.64 nm/mm fitted with ICCD detector. The spectrum consists
of 108 bands, which are classified into four new subsystems E0
u
+
(1Σ
u
+
) → A1g(3Πg), J0
g
±
\1g(3Σ
g
+
) → D1u(1Πu), F1u → A0
g
±
(3Πg) and F1u → A2g(3Πg) along with additional bands of the known system E0
u
+
(1Σ
u
+
) → A0
g
±
(3Πg). The molecular constants for these systems have also been determined. 相似文献
11.
M. D. Saksena M. N. Deo K. Sunanda S. H. Behere Ashok Jadhav 《Indian Journal of Physics》2011,85(3):485-495
The emission spectrum of the A
2
Π
r
-X
2
Σ
+ band system of MgCl molecule (360–380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution
of 0.035 cm−1. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250
mA) containing anhydrous MgCl2 and Ar. The resulting spectra are very intense and the 0-0, 1-1, 1-0 bands of A
2
Π
1/2-X
2
Σ
+ sub-transition and the 0-0 band of A
2
Π
3/2-X
2
Σ
+ sub-transition have been rotationally analyzed. Improved molecular constants have been derived using a least-squares fit
program in which optical data of earlier analyzed 0-1 and 0-2 bands (A
2
Π
1/2-X
2
Σ
+) was also included. The Λ-doubling constants in the v′ = 0, 1 levels of the A
2
Π
1/2 sub-state are as expected, i.e. p
1 > p
0, where as it is found that the spin-doubling constants of the v″ = 0, 1 and 2 levels of the ground state X
2
Σ
+, decrease with the increase in v, i.e.
γ
0 > γ
1 > γ
2. This is indicative of the presence of some nearby state, influencing the spin-doubling. 相似文献
12.
The effect of externally injected radiation on the two-photon laser-induced amplified spontaneous emission (TP-LIASE) is reported.
The wave generated via the same LIASE process in a seeder cell acts as a seeder field for the inverted medium created in a
main cell. A nearly tenfold gain is achieved in the B1
Σ
+
?A1
Π (0, 3) transition of the CO molecule. We demonstrate that the single rotational transition in the B1
Σ
+
?A1
Π (0, 4) band is selectively amplified by injection of laser radiation. This pump and seed arrangement facilitates detection
of molecular spectra by simply tuning the seed-laser frequency. The polarization effect of the input laser radiation is briefly
discussed.
Received: 9 June 2000 / Revised version: 2 October 2000 / Published online: 21 February 2001 相似文献
13.
A.T. Hartlieb D. Markus W. Kreutner K. Kohse-Höinghaus 《Applied physics. B, Lasers and optics》1997,65(1):81-91
2 Σ+) was measured in a low-pressure H2/O2 flame for three rotational levels of OH (v′=1). Rate coefficients for collisions with H2O and N2 were determined. At 1600 K, kVET (N2) is (in 10-11 cm3s-1) 10.1±2, 6.1±1.8, and 3.8±1.3 for N′=0, 5, and 13, respectively. The kVET (H2O) is <1.1±1.8. The kQ (N2) is <2.4±8 for both vibrational levels. The kQ (H2O) in v′=1 is 59.1±6.5, 54.7±6.4, and 54.9±6.6 for N′=0, 5, and 13, respectively, and, determined indirectly, 74.6±10.4, 70.6±10.3, and 63.4±7.3 for N′=0, 5, and 13 in v′=0. A multi-level model of OH population dynamics, which is being developed for the quantitative simulation of experimental
LIF spectra, was extended to include VET. It was attempted to simulate state-to-state-specific VET coefficients for N2 collisions. From these simulations it appears that angular momentum conservation does not determine the N dependence of the
vibrational relaxation step.
Received: 9 September 1996/Revised version: 6 January 1997 相似文献
14.
David J. Creasey Dwayne E. Heard Michael J. Pilling Benjamin J. Whitaker Martin Berzins Roger Fairlie 《Applied physics. B, Lasers and optics》1997,65(3):375-391
2 Σ+, v′=0) by air at 26±4 K. A value of 2.56±0.40×10-10 molecule-1 cm3 s-1 was obtained, a factor of more than four higher than at room temperature, and consistent with attractive forces dominating
the quenching of OH(A2Σ+). A d
etailed computational fluid dynamics (CFD) simulation of the supersonic free-jet expansion was performed, providing a two-dimensional
visualisation of temperature and density variations throughout the expansion. The CFD calculations reproduced the salient
features of the experimental temperature and density profiles along the centreline. Comparison between experiment and computation
has allowed validation of CFD codes.
Received: 31 January 1997/Revised version: 24 March 1997 相似文献
15.
A. A. Mikhalchenko E. V. Kartaev V. I. Kuzmin V. I. Nalivaiko P. A. Chubakov 《Thermophysics and Aeromechanics》2011,18(4):629-641
Results of application of a method for measuring the distribution of temperature in a nitrogen plasma jet emanating from a
dc plasma torch with sectioned inter-electrode insert from the relative intensities of the molecular emission bands of nitrogen
in the N2
+(B2Σu
+ − X2Σg
+) first negative and N2(C3Πu
+ − B3Πg
+) second positive systems are reported. The emission spectra were registered using a small-size spectrometer with medium-range
spectral resolution enabling a contour analysis of ro-vibrational bands in molecular emission spectra. The obtained distribution
of temperature was compared with the distribution that was determined from the emission lines due to copper atoms and with
the mean-mass plasma temperature of the air plasma jet. 相似文献
16.
W. Szajna M. Zachwieja 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(3):549-555
The high-resolution emission spectrum of the A1
Π–X1Σ+ transition of AlH was observed in the 18 000–25 000 cm-1 spectral region using a conventional spectroscopic
technique. The AlH molecules were excited in an Al hollow-cathode
lamp filled with a mixture of Ne carried gas and a trace amount of
NH3. The emission from the discharge was observed with a plane
grating spectrograph and recorded by a photomultiplier tube. In
total 163 transition wave numbers belonging to six bands (0-0,1
and 1-0,1,2,3) were precisely measured and rotationally
analysed. In the final fit the present data have been combined
with available high-resolution measurements of the
vibration-rotation bands by White et al. [J. Chem. Phys. 99,
8371 (1993)]. This procedure enabled extracting molecular
constants for the A1
Π and X1
Σ+ states of AlH. A very
slight local perturbation has been discovered in the v=1
vibration level of the A1
Π state at J=5. This was probably
caused by the interaction with the a3Π state. 相似文献
17.
W. Hubschmid 《Applied physics. B, Lasers and optics》2009,94(2):345-353
Laser-induced gratings in mixtures of O2 with CO2 were formed by excitation of the O2 molecules to the singlet state b
1
Σ
g
+(v′=0). Density changes from heat release and from electrostriction, and variation of electric polarizability by excitation
of molecules contribute to the grating. For modeling the relaxation of the excited O2 molecules, a three-step process is assumed: Fast heat release with respect to the rotational states first, then medium fast
electronic de-activation with excitation of vibrational states of the O2 and CO2 molecules, and then the final slow heat release processes. The observed temporal evolution of the diffraction efficiency
of the grating agrees rather well with modeling. Average rates of the final relaxations and the value of the polarizability
of the singlet state b
1
Σ
g
+(v′=0) are determined in this way. 相似文献
18.
A. I. Reznikov S. Ya. Umanskii Yu. F. Chaikina 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(2):203-209
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. 相似文献
19.
20.
A. Brockhinke A.T. Hartlieb K. Kohse-Höinghaus D.R. Crosley 《Applied physics. B, Lasers and optics》1998,67(5):659-665
2 in a flame, excited by a tunable KrF laser near 248 nm. The first comprises several P and R lines of the (1,0) band of the
e 3Πg-a 3Πu Fox–Herzberg system, with fluorescence bands extending past 350 nm. The second is the band head region of the (7,1) band
of the D 1Σu
+←B′ 1Σg
+ system, with fluorescence at 232 nm from D to the X 1Σg
+ ground state. Neither band has been previously observed in any environment. The flame in these experiments is highly sooting,
and the C2 seen here is likely produced by laser vaporization of the soot with subsequent laser photolysis of a C2 precursor. In a rich flame, this fluorescence could cause interferences in other studies such as KrF laser Raman scattering.
Moreover, signal level calculations suggest native C2 near 10 ppm could be readily observed using the Fox–Herzberg excitation. Raman measurements of major species (X≥0.01) in
the same flame, using the KrF laser, are in good agreement with a model prediction.
Received: 2 April 1998/Revised version: 8 June 1998 相似文献