High-Order Resonance Interactions in HDO: Analysis of the Absorption Spectrum in the 14 980-15 350 cm(-1) Spectral Region

The absorption spectrum of the HDO molecule recorded by intracavity laser absorption spectroscopy in the 14 980-15 350 cm(-1) spectral region was assigned and modeled in the frame of the effective Hamiltonian approach. The spectrum (496 lines) results, mainly, from transitions to the rotational sublevels of the (014) bright state. An important number of transitions involving the (142) and (0 12 0) highly excited bending states could be identified, borrowing their intensities through high-order resonance interactions with the (014) state. An original feature shown by the present analysis is that all the transitions involving unperturbed energy levels of the (014) state are exclusively of A type, while both A- and B-type transitions are observed when the upper states are perturbed by the resonance interactions. One hundred forty-five energy levels of the three interacting states were derived from the spectrum and fitted to the effective rotational Hamiltonian in Pade-Borel approximants form with 29 varied parameters yielding an rms deviation of 0.038 cm(-1). A few energy levels are affected by additional local resonances with perturbers which have been identified. Finally, 48 transitions of the very weak 6nu(1) band were assigned and fitted as an isolated band. Copyright 2000 Academic Press.     

Experimental and Ab Initio Studies of the HDO Absorption Spectrum in the 13 165-13 500 cm(-1) Spectral Region

The HDO absorption spectrum was recorded in the 13 165-13 500 cm(-1) spectral region by intracavity laser absorption spectroscopy. The spectrum (615 lines), dominated by the 2nu(2) + 3nu(3) and nu(1) + 3nu(3) bands, was assigned and modeled leading to the derivation of 196 accurate energy levels of the (103) and (023) vibrational states. Finally, 150 of these levels were reproduced by an effective Hamiltonian involving two vibrational dark states interacting with the (023) and (103) bright states. The rms deviation achieved by variation of 28 parameters is 0.05 cm(-1), compared to an averaged experimental uncertainty of 0.007 cm(-1), indicating the limit of validity of the effective Hamiltonian approach for HDO at high-vibrational excitation. The predictions of previous ab initio calculations of the HDO spectrum (H. Partridge and D. Schwenke, J. Chem. Phys. 106, 4618-4639 (1997)) were extensively used in the assignment process. The particular spectral region under consideration was used to test and discuss the improvements of new ab initio calculations recently performed on the basis of the same potential energy surface but with an improved dipole-moment surface. The improvements concern both the energy levels and the line intensities. In particular, the strong hybrid character of the nu(1) + 3nu(3) band is very well accounted for by the new ab initio calculations. Copyright 2000 Academic Press.     

Jet-Cooled Optical Spectroscopy of FeN between 16 300 and 21 600 cm(-1)

We report the first gas-phase spectroscopic study of iron mononitride (FeN). FeN molecules were generated by the reaction of laser-ablated Fe atoms with NH(3) under supersonic jet-cooled conditions. Laser-induced fluorescence excitation spectra were measured between 16 300 and 21 600 cm(-1), and rotational analyses have been performed for about 25 vibronic bands. The Omega value of the ground state has been determined to be 52, which could be the spin-orbit component of (2)Delta (ellipsis 1delta(3)9varsigma(2)) or (4)Pi (ellipsis 1delta(3)9varsigma(1)4pi(1)). The excited states in the visible absorption region show very complicated rovibronic structures due to heavy perturbations. Excited state lifetimes, (56)Fe(14)N/(56)Fe(15)N isotope shifts, and dispersed fluorescence spectra were measured for the majority of the bands, which were classified into the five Omega = 52-XOmega = 52 band systems. Copyright 2000 Academic Press.     

Near-Infrared Spectrum (3000-10 000 cm) of 4-Chlorophenol in Solution

The near-infrared spectra (3000-10 000 cm⁻¹) of 4-chlorophenol-OH and 4-chlorophenol-OD are studied at room temperature in carbon tetrachloride. Some data are also reported for 4-bromophenol-OH and 4-bromophenol-OD. The observed absorptions are assigned to overtones or combinations involving the fundamental transitions which have been recently calculated at the B3LYP/6-311++G(df,pd) level (J. Phys. Chem. A104, 11 685 (2000)). The anharmonicities and the harmonic frequencies of the local ν(OH) and ν(CH) modes and the coupling constants for the binary or ternary combinations are obtained. The extinction coefficients of these transitions are discussed. The half-band width of the ν(OH) and ν(CH) vibrations increases with the absorption frequencies. The experimental harmonic frequencies are obtained from the anharmonicity constants. Comparison with the theoretical frequencies indicates that the low scaling factors ranging from 0.950 to 0.960 characterizing the ν(OH) and ν(CH) vibrations can be accounted for by the large anharmonicity of these vibrations. For these vibrations, the ratio of the experimental harmonic frequencies to the computed frequencies is 0.993. This value does not significantly differ from the average scaling factors of 0.987-0.989 obtained for all the other vibrational modes.     

High-Resolution Study of Strongly Interacting Vibrational Bands of HDO in the Region 7600-8100 cm(-1)

The high-resolution Fourier transform spectrum of the HDO molecule was recorded and analyzed in the region 7600-8100 cm(-1) where the weak vibration-rotation bands 3nu(1) and nu(1) + nu(2) + nu(3) are located. Because of the presence of strong local resonance interactions, transitions belonging to the 3nu(2) + nu(3) and 6nu(2) bands were assigned as well. Spectroscopic parameters of all four bands were estimated, which reproduce initial line positions with accuracy close to experimental uncertainties. Copyright 2000 Academic Press.     

Absorption Spectrum of H2O in the Range 12 400-14 520 cm

Fourier transform spectra recorded using (a) natural abundance water vapor, (b) H₂¹⁸O-enriched water vapor, and (c) H₂¹⁷O-enriched water vapor are analyzed. The ratio of intensities in three spectra is used to identify 927 lines due to absorption by H₂¹⁸O. Intensities and self-broadening parameters are derived for these lines. Using theoretical linelists, comparisons with previously assigned H₂¹⁶O spectra, and automatic searches for combination differences, 747 lines are assigned. These lines belong to 14 vibrational states in the 3ν+δ and 4ν polyads. Newly determined H₂¹⁸O vibrational band origins include 4ν₁ at 13 793.09 cm⁻¹, 3ν₁+ν₃ at 13 795.40 cm⁻¹, 2ν₁+2ν₃ at 14 188.82 cm⁻¹, ν₁+3ν₃ at 14 276.34 cm⁻¹, and 2ν₂+2ν₂+ν₃ at 13 612.71 cm⁻¹. These results are compared with data in HITRAN.     

High-resolution ro-vibrational spectroscopy of HDO in the region of 8900-9600 cm

The high-resolution absorption spectrum of the HDO molecule was recorded with a Fourier-transform interferometer in the region of 8900-9600 cm⁻¹, where the strongly interacted bands 2ν₁ + ν₃, 3ν₁ + ν₂, ν₁ + 2ν₂ + ν₃, 2ν₁ + 3ν₂, 4ν₂ + ν₃, ν₁ + 5ν₂, and 7ν₂ are located. About 1000 transitions were assigned to these seven bands based on the ab initio predictions [J. Chem. Phys. 106 (1997) 4618]. Altogether, 375 upper energy levels were determined, including 24 energy levels of the highly excited bending (070) state. On that basis, the necessity of the “Effective Hamiltonian” concept in the spectroscopic analysis is discussed.     

High-Resolution Spectrum and Rovibrational Analysis of the nu(2)/nu(5) Dyad of D(3)SiF near 700 cm(-1)

The nu(2) (A(1), 710.157 cm(-1)) and nu(5) (E, 701.717 cm(-1)) fundamental bands of D(3)(28)SiF have been studied by FTIR spectroscopy with a resolution of 2.4 x 10(-3) cm(-1). We assigned 1648 lines for the parallel band (J(max) = 50, K(max) = 21), 4279 for the perpendicular band (J(max) = 52, K(max) = 27), and in addition 671 perturbation-allowed transitions (J(max) = 50, K(max) = 12). The nearly degenerate v(2) = 1 and v(5) = 1 states are linked by (DeltaK = +/-1, Deltal = +/-1) and (DeltaK = +/-2, Deltal = -/+1) interactions, while the l(5) = +/-1 levels of nu(5) interact also by l(2, -1), l(2, 2), and l(2, -4) interactions. The first model with 36 free parameters, taking into account all these resonances through a nonlinear least-squares program, gave standard deviations of 1.56 x 10(-4) cm(-1) for 5997 nonzero-weighted IR data and 138 kHz for 8 MW data from the literature. The second model, in which the main Coriolis term was constrained to a force field value, used 37 parameters and gave similar standard deviations. A new determination of the A(0) and D(0)(K) ground state parameters was performed by two methods: either using differences between "forbidden" transitions differing by 3 in K or letting A(0) and D(0)(K) free in the global fit. The values obtained are fully compatible with those obtained previously by the "loop method." Copyright 2000 Academic Press.     

Line parameters of HDO from high-resolution Fourier transform spectroscopy in the 11 500-23 000 cm spectral region

This work presents new measurements of HDO line parameters in the near-infrared and visible regions (11 500-23 000 cm⁻¹). The measurements consist in high-resolution Fourier transform absorption spectra of H₂O/HDO/D₂O vapor mixtures, obtained using a long absorption path. Spectra with and without nitrogen as the buffer gas were recorded. Due to the simultaneous presence of the three isotopologues H₂O, D₂O, and HDO, the H₂O lines removal and the D₂O lines identification were two necessary preliminary steps to derive the HDO line parameters. The D₂O contribution was small and confined to the well-known 4ν₁ + ν₃ band. An extensive listing of HDO spectroscopic parameters was obtained, for the first time, by fitting some 3256 observed lines to Voigt line profiles. The list contains calibrated line positions, absorption cross-sections and, for many of the lines, N₂-broadening coefficients, as well as N₂-induced frequency shifts. As a result of the low HDO vapor pressures, it was not possible to retrieve the self-broadening parameters. The list is available on the http://www.ulb.ac.be/cpm website.     

FT Infrared Spectra of FCN from 1200 to 1800 cm(-1) and from 2800 to 7000 cm(-1) and Global Rovibrational Analysis of the Main Isotopomers

We measured the FT spectrum of natural FCN from 1200 to 1800 cm(-1) and from 2800 to 7000 cm(-1) with a near Doppler resolution and a line-position accuracy between 1 and 8 x 10(-4) cm(-1). Lines were assigned to 91 different bands (75 of (19)F(12)C(14)N, 11 of (19)F(13)C(14)N, and 5 of (19)F(12)C(15)N), of which no more than five had been previously reported at lower resolution. From band-by-band analyses we deduced effective state parameters. As those results complete the study of the Fourier transform spectra of natural cyanogen fluoride from 1200 to 7000 cm(-1), global rovibrational analyses of (19)F(12)C(14)N, (19)F(13)C(14)N, and (19)F(12)C(15)N have been performed on the basis of all the available experimental data about their rovibrational energies. We have so determined sets of about 100 molecular parameters for each isotopomer, and a statistical agreement was obtained. A labeling of the vibrational states is proposed on the basis of the eigenvector coefficients. Copyright 2000 Academic Press.     

High-Resolution Infrared Spectrum of BrCN in the nu(2) and nu(1)/2nu(2) Regions

The vibrational excitations of bent triatomic molecules, including both bending and stretching vibrations, are studied in the framework of the U(4) algebra. For the bent triatomic molecules H(2)O and H(2)S, the highly excited vibrational levels (up to 14) are obtained using the U(4) algebraic approach. We have found that the spectra are made up of clustering structure. The number of levels in one cluster depends on the total quanta of stretching and bending. In addition, some other properties are also discussed. Copyright 2000 Academic Press.     

High resolution Fourier transform spectrum of HDO in the 7500-8200 cm region: revisited

The HDO absorption FT spectrum is recorded and analyzed in the 7500-8200 cm⁻¹ spectral region. The high accuracy ab initio calculation of Schwenke and Partridge was successfully applied for spectrum assignment that resulted in derivation of 508 precise rovibrational energy levels for the (3 0 0), (0 3 1), (1 1 1), (0 6 0), (2 2 0), and (0 0 2) states, with 295 of them being reported for the first time. In particular, eight new energy levels, including the band center at 7914.3170 cm⁻¹, were derived for the highly excited bending (0 6 0) state from transitions borrowing their intensities through local high-order resonance coupling with the (3 0 0) and (0 3 1) states.     

Rovibrational and Rotational Spectroscopy of Levels of Propyne around 1000 cm(-1)

Four vibrational levels in the energy region around 1000 cm(-1) were studied. These were the v(5)=1 and v(8)=1 fundamental levels, both components of the v(9)=v(10)=1 combination level (l(9)=l(10)=+/-1 and l(9)=-l(10)=+/-1), and both components of the v(10)=3 overtone level (l(10)=+/-1 and +/-3). New FTIR spectra with a synchrotron radiation source were recorded in the region of the "superhot" v(10)=3<--2 bands, which made possible the first assignment of levels of the v(10)=3(+/-1) sublevel. More than 330 new rotational transitions in the combination and overtone levels were measured by millimeter-wave spectroscopy betwen 50 and 360 GHz. The new data were analyzed simultaneously together with the previously assigned rovibrational data for the fundamental and combination levels and rotational data for the fundamental levels using a global model with all anharmonic, Coriolis, l-type, and alpha-resonances. Significant improvement of data reproduction and very good consistency with the Hamiltonian parameters of the lower vibrational levels v(9)=1 and v(10)=1, 2 were achieved. A strong dependence of the A(v) constant on the l(10) quantum number is found for propyne: this is shown to be characteristic of skeleton C-C identical withC or C-C identical withN bending modes in H(3)CCCH, H(3)CCN, and their fully deuterated species. Copyright 2001 Academic Press.     

The (22(0)1-00(0)0) Band of CO(2) at 6348 cm(-1): Linestrengths, Broadening Parameters, and Pressure Shifts

The (22(0)1-00(0)0) combination band of CO(2) around 6348 cm(-1) is studied with diode-laser spectroscopy, and linestrengths, collision-broadening parameters, and pressure shifts are determined. Linestrengths are modeled with a third-order Herman-Wallis expansion, and discrepancies with values reported in the literature are explained. Copyright 2000 Academic Press.     

76500～81120cm~(-1)范围内碘甲烷分子的双光子电离光谱

在离子速度成像的实验装置中,将波长为492~523 nm范围内的激光倍频,以经过倍频的激光作光源,将碘甲烷分子(CH3I)电离,获得了碘甲烷母体分子离子(CH3I+)在76 500~81 120 cm-1范围内的高分辨双光子电离光谱;介绍了CH3I的双光子电离机制,根据Rydberg公式和量子数亏损成功对实验所得到的CH3I+谱中的46个谱峰做了标识,并观察到了CH3I+谱中p,d,f系列的能级分裂。标识结果表明,在CH3I的双光子电离谱中除了可以观察到单光子电离谱的特征,还可以观察到在单光子电离中禁阻的f系列跃迁。     

离体正常乳腺组织350～850 nm波段光谱特性

采用带有积分球附件的紫外/可见/近红外分光光度计测量了离体正常乳腺组织在350～850 nm光谱范围的反射率和透射率,运用反向倍加法得到了离体正常乳腺组织在相应光谱范围的光学参数,分析了正常乳腺组织的光学穿透深度随波长的变化情况。实验结果表明：350～850 nm波段正常乳腺组织的约化散射系数μ′_s大于吸收系数μ_a。μ′_s随着波长的增加而减小,即从350 nm波长值为9.731 mm-1～850 nm波长值为1.476 mm-1。μ_a从350 nm波长值为0.798 mm-1～850 nm波长值为0.102 mm-1,410 nm波长处存在一个吸收峰,其值为0.506 mm-1。光学穿透深度随着波长的增加而增大,从350 nm波长值为0.199 mm-1～850 nm波长值为1.439 mm。基于反向倍加法计算获得乳腺组织的光学参数,采用Monte Carlo模拟得到其相应光谱范围的反射率和透射率,并与实际测量值进行比较,二者的一致性较好。实验结果为乳腺组织的光活检及其光学治疗提供重要参考。