A precise study of the rotational spectrum of formaldehyde H2CO, H2CO, H2CO, H2CO

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

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Observation of hot bands in the infrared spectrum of H2CO

Two hot bands in the infrared spectrum of formaldehyde (H₂CO) have been identified by means of tunable infrared laser spectroscopy using a jet-cooled sample. One band falls in the region 2760-2800 cm⁻¹; it follows a-type selection rules and it has been assigned as the ν₁ + ν₄ − ν₄ hot band. The other band falls in the region 2800-2860 cm⁻¹; it follows b-type selection rules and it has been assigned as the ν₅ + ν₄ − ν₄ hot band. The observations are restricted to low J and K_a levels. It has consequently been possible to ignore the effects of the extensive Coriolis couplings involving these levels in the analysis of the spectra and to model the rotational structure as that of a simple asymmetric top. Least-squares fits of the data have provided values for the band origins: 2774.2706(11) cm⁻¹ for the ν₁ + ν₄ − ν₄ and 2829.2621(8) cm⁻¹ for the ν₅ + ν₄ − ν₄ band. Term values for the upper vibrational levels involved in the transitions have been determined by use of the previously reported term values for the v₄ = 1 level.     

ΔK = 2 transitions in H2CO and D2CO

Weak transitions of the type ΔJ = ± 1, $\text{Δ}\text{K}{}_{\mathrm{a}}\text{= ? 2}$, ΔK_c = ± 3 have been observed in H₂CO and D₂CO by the millimeterwave double resonance method and also by direct absorption with a Stark modulated spectrometer. The addition of these new transitions in a least-squares analysis, in which all previously known microwave and millimeterwave data are also included, results in an improved set of rotational and distortion constants.     

The microwave spectrum of cyanophosphine, H2PCN

The rotational spectra of cyanophosphine, H₂PCN, have been measured between 10 and 42.5 GHz by Fourier transform microwave spectroscopy. The rotational constants, centrifugal distortion constants, the ¹⁴N quadrupole coupling constant, and the nuclear spin-rotation coupling constants of ³¹P have been determined. Density functional ab initio calculations were performed, and the calculated values of the molecular constants are in excellent agreement with our experimentally determined results. The spectra of three isotopomers were measured, H₂P¹²C¹⁴N, H₂P¹³C¹⁴N, and H₂P¹²C¹⁵N. The derived r₀ structure is quite comparable to the ab initio predicted H₂PCN equilibrium geometry.     

The microwave spectrum of cyanophosphaacetylene, H2PCCCN

The a type transitions of the microwave rotational spectra of cyanophosphaacetylene, H₂PCCCN, have been investigated in the frequency region between 5 and 26.5 GHz by Fourier transformation microwave (FTMW) spectroscopy. Rotational, centrifugal distortion and ¹⁴N nuclear quadrupole coupling constants have been determined. Density functional theory level ab initio calculations were performed to predict the molecular constants, and the predicted values are in good agreement with our experimentally determined results. The ¹³C and ¹⁵N isotopomer transitions were also observed. The derived r₀ structure is quite comparable to the calculated H₂PCCCN equilibrium geometry.     

The magnetic hyperfine structure in the rotational spectrum of H2CNH

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the ¹⁴N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters.     

Comments on the microwave absorption spectrum of solid H2

Recent theories by Luryi et al. and by Harris et al. for the energy levels of an isolated pair of ortho-H₂ molecules in nearly pure solid para hydrogen are compared.     

Stark spectroscopy with the CO laser: The ν2 fundamentals of H2CO and D2CO

The ν₂ (CO stretching) vibration-rotation bands of H₂CO and D₂CO near 5.8 μm have been studied using the technique of laser Stark spectroscopy. The following vibrational and rotational constants have been determined:

     

9.

The ν₂ fundamental band of H₂CO     

C. Bréchignac  J.W.C. Johns  A.R.W. McKellar  M. Wong 《Journal of Molecular Spectroscopy》1982,96(2):353-361

The ν₂ fundamental band of H₂CO has been studied using a combination of sub-Doppler laser Stark spectroscopy and Doppler-limited Fourier transform spectroscopy. A combined analysis of the Stark and Fourier infrared data together with previous microwave data on the ν₂ = 1 state yielded improved molecular parameters for formaldehyde, including the excited state dipole moment. A small perturbation was noted at K′_a = 7 which may be ascribed to a ΔK_a = 2 interaction with the v₃ = 1 state. Precise treatments of ν₂ with K′_a > 6 will thus require a combined analysis taking into account Coriolis interactions among ν₄, ν₆, ν₃, and ν₂.     

10.

High resolution pure rotational spectrum of water vapor enriched by H₂¹⁷O and H₂¹⁸O     

J. Kauppinen  E. Kyrö 《Journal of Molecular Spectroscopy》1980,84(2):405-423

The pure rotational spectrum of a mixture of H₂¹⁶O, H₂¹⁷O and H₂¹⁸O between 50 and 730 cm^?1 was recorded on the Fourier transform spectrometer at the University of Oulu. The resolution achieved was about 0.010 cm^?1 and the precision of the unblended lines was better than 0.001 cm^?1. About 1100 lines were assigned. The measured line positions of H₂¹⁷O and H₂¹⁸O were compared with the values derived from the rotation and distortion constants given in the literature.     

11.

Measurement of H₂CO hyperfine structure with a two-cavity maser     

S.G. Kukolich  D.J. Ruben 《Journal of Molecular Spectroscopy》1971

Hyperfine structure on the 1₁₀ → 1₁₁ rotational transition in H₂CO was measured using a two-cavity maser spectrometer with 0.3 kHz resolution. The measured spin-rotation constants are C(1₁₀) = −0.80 ± 0.05 kHz and C(1₁₁) = −3.07 ± 0.05 kHz. The hydrogen spin-spin interaction strength is D = 17.74 ± 0.10 kHz. The line center is at 4 829 659.89 ± 0.12 kHz. Properties of the beam source and computer line resolving methods are discussed briefly.     

12.

A precise study of the rotational spectrum of formaldehyde H₂¹²C¹⁷O and H₂¹³C¹⁷O     

R. Cornet  B.M. Landsberg  G. Winnewisser 《Journal of Molecular Spectroscopy》1980,82(2):253-263

The pure rotational spectra of H₂¹²C¹⁷O and H₂¹³C¹⁷O have been investigated in the frequency region between 8 and 360 GHz in the ground vibrational state. For both isotopic species the ¹⁷O nuclear quadrupole coupling constants and spin-rotation constants have been obtained. From both Q- and R-branch transitions a set of rotational constants and several distortion constants could be derived employing Watson's formalism in A reduction. The obtained rotational constants are in Megahertz:

Constant	H2CO	D2CO	Unit
$\text{ν}{}_0$	1746.011	1701.620	cm?1
$\text{A′}$	281807.8 ± 6.	141696.6 ± 7.	MHz
$\text{B′}$	38608.7 ± 5.	32068.4 ± 7.	MHz
$\text{C′}$	33738.7 ± 3.	25998.6 ± 10.	MHz
μ″	2.328 ± 0.006	2.344 ± 0.006	Debye
μ′	2.344 ± 0.006	2.364 ± 0.005	Debye

     

13.

Revised ultraviolet absorption cross sections of H₂CO for the HITRAN database     

K. Chance  J. Orphal 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(9):1509-1510

A revised set of temperature-dependent absorption cross sections for ultraviolet (UV) measurements of formaldehyde (H₂CO) has been derived from two existing sets of laboratory cross sections, one using a Fourier transform spectrometer (FTS), and one using a grating instrument. This is conducted to satisfy the recommendation of the HITRAN Advisory Committee to provide a dataset with the spectral resolution and wavelength calibration of Fourier transform spectrometer measurements with the better intensity calibration that the grating measurements obtained. The re-scaled cross sections are now in the HITRAN database, and are recommended for use in atmospheric measurements and modeling, including photolysis calculations.     

14.

A precise study of the rotational spectrum of formaldehyde H₂¹²C¹⁶O,H₂¹³C¹⁶O,H₂¹²C¹⁸O,H₂¹³C¹⁸O     

R. Cornet  G. Winnewisser 《Journal of Molecular Spectroscopy》1980,80(2):438-452

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

	H212C17O	H213C17O
$\text{A}$	281 965.0 (30)	281 987.3 (19)
$\text{B}$	37 812.287(45)	36 776.790(25)
$\text{C}$	33 214.523(31)	32 412.920(19)

     

15.

The oxidation of H₂CO on a copper(110) surface     

Israel E. Wachs  Robert J. Madix 《Surface science》1979,84(2):375-386

The oxidation of H₂C¹⁶O by adsorbed ¹⁸O was studied on an Cu(110) sample by temperature programmed reaction spectroscopy. Formaldehyde exchanged its oxygen with surface ¹⁸O upon adsorption to yield H₂C¹⁸O_(a) and ¹⁶O_(a). Formaldehyde was also oxidized by surface ¹⁶O and ¹⁸O atoms to H₂COO which subsequently released one of the hydrogen atoms to form HCOO. The evolution of H₂ from the Cu(110) surface was desorption limited, and the low pre-exponential factor for the recombination of the surface hydrogen atoms suggested stringent requirement on the trajectories of the colliding partners. The formate was very stable and dissociated at elevated temperatures to simultaneously yield H₂ and CO₂. The surface concentration of ¹⁸O exerted a pronounced affect on the activity of the oxidation of formaldehyde on Cu(110).     

16.

Microwave spectrum of the heterodimers: CH₃OH-CO₂ and CH₃OH-H₂CO     

V.V. Ilyushin  F.J. Lovas 《Journal of Molecular Spectroscopy》2006,239(1):94-100

Molecular complexes, dimers and heterodimers often show interesting structures, large amplitude internal motions and orientations for reaction coordinates. These properties were the motivations for the current study of the rotational spectra of the heterodimers, CH₃OH-CO₂ and CH₃OH-H₂CO, in a pulsed nozzle Fourier-transform microwave (FTMW) spectrometer. In addition to studying the normal isotopic forms, several isotopologues containing ¹³C or deuterium substituted atoms of each heterodimer were analyzed in order to obtain structural data of the complexes. All species showed splittings from internal rotation of the methyl group and splittings on the b-type transitions of the CH₃OH-H₂CO species suggesting rotation of the H₂CO group between equivalent structural forms. Stark effect measurements on each of the parent species provided dipole moment components. Theoretical ab initio results are compared to the experimentally determined molecular parameters.     

17.

Microwave spectrum of isotopic species of urea (NH₂)₂CO     

S. Kassi 《Journal of Molecular Spectroscopy》2004,228(2):293-297

We report new microwave measurements for the (¹⁵NH₂)₂CO and (¹⁴NH₂) (¹⁵NH₂)CO isotopologues of urea. The spectra were recorded between 5 and 20 GHz with our MWFT spectrometer coupled to a newly built heated nozzle. A new centrifugal distortion analysis was performed for the (¹⁵NH₂)₂CO species including all available data. For the (¹⁴NH₂) (¹⁵NH₂)CO species the hyperfine structure was recorded for the first time.     

18.

H2SiCl2 中 SiH 伸缩振动的泛频光谱          下载免费PDF全文

陈平  朱淮  郝绿原  胡水明  刘安雯  郑晶晶  丁昀 《中国物理》2005,14(3):634-641

在2000 ～ 9000 波数 、 12000 ～12900 波数的光谱区间记录了室温下H2SiCl2气体分子的振动泛频光谱，所用的仪器分别是高分辨傅立叶变换光谱仪和高灵敏激光腔内吸收光谱仪。用局域模模型和包含达林－丹尼生共振的简正模模型，归属了SiH伸缩振动的基频和泛频，振动量子数的改变△VSiH=1, 2, 3, 4 and 6。通过对实验能级的非线性拟合，得到SiH伸缩振动的谐振频率ωm、非谐性常数χm、键间耦合系数λ、莫尔斯振子参数 De、α 和相互作用力常数 。实验发现，随着振动能量的增加，振动簇（manifold，两个SiH键的伸缩振动量子数m+n=常数 ）中能量最低的两个能级的间距逐渐减小。当△VSiH≥4时，在实验误差范围内这两个最低的振动态能级简并。这种简并的能级结构类似双原子莫尔斯振子，符合Birge-Sponer 关系。双原子莫尔斯振子直接描述了H2SiCl2分子中SiH 的高泛频伸缩振动，表明在高振动情况下振动能量已经集中到单个SiH键上。     

19.

Reaction products from a discharge of N₂ and H₂S: The microwave spectrum of NH₂SH     

F. J. Lovas  R. D. Suenram  W. J. Stevens 《Journal of Molecular Spectroscopy》1983,100(2):316-331

Thiohydroxylamine has been identified as one of the reaction products from the discharge reaction of N₂ + H₂S. Both cis and trans conformers have been observed. The rotational spectra have been studied from 56 to 170 GHz for the normal species and several deuterated isotopic species of each conformer. The electric dipole moments of both conformers have been determined. A number of the transitions of the cis conformer exhibit splittings due to the nuclear quadrupole moment of the ¹⁴N nucleus. A least squares fit of the frequency splittings have led to an analysis of the eQq values. Ab initio calculations using a 4-31G basis set both with and without polarization functions have been carried out to aid in the analysis and to provide a final structural comparison with the microwave results.     

20.

Centrifugal distortion analysis of pure rotational spectra of H₂¹⁶O,H₂¹⁷O,and H₂¹⁸O     

E. Kyrö 《Journal of Molecular Spectroscopy》1981,88(1):167-174

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

	H212C16O	H213C16O	H212C18O	H213C18O
A/MHz	281 970.572 (24)	281 993.258(135)	281 961.94 (39)	281 985.00 (93)
B/MHz	38 836.0456(13)	37 811.0887(25)	36 904.1693(66)	35 859.256(10)
C/MHz	34 002.2034(12)	33 213.9790(25)	32 511.5311(63)	31 697.868(10)

The ν2 fundamental band of H2CO

The ν₂ fundamental band of H₂CO has been studied using a combination of sub-Doppler laser Stark spectroscopy and Doppler-limited Fourier transform spectroscopy. A combined analysis of the Stark and Fourier infrared data together with previous microwave data on the ν₂ = 1 state yielded improved molecular parameters for formaldehyde, including the excited state dipole moment. A small perturbation was noted at K′_a = 7 which may be ascribed to a ΔK_a = 2 interaction with the v₃ = 1 state. Precise treatments of ν₂ with K′_a > 6 will thus require a combined analysis taking into account Coriolis interactions among ν₄, ν₆, ν₃, and ν₂.     

High resolution pure rotational spectrum of water vapor enriched by H217O and H218O

The pure rotational spectrum of a mixture of H₂¹⁶O, H₂¹⁷O and H₂¹⁸O between 50 and 730 cm^?1 was recorded on the Fourier transform spectrometer at the University of Oulu. The resolution achieved was about 0.010 cm^?1 and the precision of the unblended lines was better than 0.001 cm^?1. About 1100 lines were assigned. The measured line positions of H₂¹⁷O and H₂¹⁸O were compared with the values derived from the rotation and distortion constants given in the literature.     

Measurement of H2CO hyperfine structure with a two-cavity maser

Hyperfine structure on the 1₁₀ → 1₁₁ rotational transition in H₂CO was measured using a two-cavity maser spectrometer with 0.3 kHz resolution. The measured spin-rotation constants are C(1₁₀) = −0.80 ± 0.05 kHz and C(1₁₁) = −3.07 ± 0.05 kHz. The hydrogen spin-spin interaction strength is D = 17.74 ± 0.10 kHz. The line center is at 4 829 659.89 ± 0.12 kHz. Properties of the beam source and computer line resolving methods are discussed briefly.     

A precise study of the rotational spectrum of formaldehyde H212C17O and H213C17O

The pure rotational spectra of H₂¹²C¹⁷O and H₂¹³C¹⁷O have been investigated in the frequency region between 8 and 360 GHz in the ground vibrational state. For both isotopic species the ¹⁷O nuclear quadrupole coupling constants and spin-rotation constants have been obtained. From both Q- and R-branch transitions a set of rotational constants and several distortion constants could be derived employing Watson's formalism in A reduction. The obtained rotational constants are in Megahertz:

Revised ultraviolet absorption cross sections of H2CO for the HITRAN database

A revised set of temperature-dependent absorption cross sections for ultraviolet (UV) measurements of formaldehyde (H₂CO) has been derived from two existing sets of laboratory cross sections, one using a Fourier transform spectrometer (FTS), and one using a grating instrument. This is conducted to satisfy the recommendation of the HITRAN Advisory Committee to provide a dataset with the spectral resolution and wavelength calibration of Fourier transform spectrometer measurements with the better intensity calibration that the grating measurements obtained. The re-scaled cross sections are now in the HITRAN database, and are recommended for use in atmospheric measurements and modeling, including photolysis calculations.     

A precise study of the rotational spectrum of formaldehyde H212C16O,H213C16O,H212C18O,H213C18O

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

The oxidation of H2CO on a copper(110) surface

The oxidation of H₂C¹⁶O by adsorbed ¹⁸O was studied on an Cu(110) sample by temperature programmed reaction spectroscopy. Formaldehyde exchanged its oxygen with surface ¹⁸O upon adsorption to yield H₂C¹⁸O_(a) and ¹⁶O_(a). Formaldehyde was also oxidized by surface ¹⁶O and ¹⁸O atoms to H₂COO which subsequently released one of the hydrogen atoms to form HCOO. The evolution of H₂ from the Cu(110) surface was desorption limited, and the low pre-exponential factor for the recombination of the surface hydrogen atoms suggested stringent requirement on the trajectories of the colliding partners. The formate was very stable and dissociated at elevated temperatures to simultaneously yield H₂ and CO₂. The surface concentration of ¹⁸O exerted a pronounced affect on the activity of the oxidation of formaldehyde on Cu(110).     

Microwave spectrum of the heterodimers: CH3OH-CO2 and CH3OH-H2CO

Molecular complexes, dimers and heterodimers often show interesting structures, large amplitude internal motions and orientations for reaction coordinates. These properties were the motivations for the current study of the rotational spectra of the heterodimers, CH₃OH-CO₂ and CH₃OH-H₂CO, in a pulsed nozzle Fourier-transform microwave (FTMW) spectrometer. In addition to studying the normal isotopic forms, several isotopologues containing ¹³C or deuterium substituted atoms of each heterodimer were analyzed in order to obtain structural data of the complexes. All species showed splittings from internal rotation of the methyl group and splittings on the b-type transitions of the CH₃OH-H₂CO species suggesting rotation of the H₂CO group between equivalent structural forms. Stark effect measurements on each of the parent species provided dipole moment components. Theoretical ab initio results are compared to the experimentally determined molecular parameters.     

Microwave spectrum of isotopic species of urea (NH2)2CO

We report new microwave measurements for the (¹⁵NH₂)₂CO and (¹⁴NH₂) (¹⁵NH₂)CO isotopologues of urea. The spectra were recorded between 5 and 20 GHz with our MWFT spectrometer coupled to a newly built heated nozzle. A new centrifugal distortion analysis was performed for the (¹⁵NH₂)₂CO species including all available data. For the (¹⁴NH₂) (¹⁵NH₂)CO species the hyperfine structure was recorded for the first time.     

H2SiCl2 中 SiH 伸缩振动的泛频光谱

在2000 ～ 9000 波数 、 12000 ～12900 波数的光谱区间记录了室温下H2SiCl2气体分子的振动泛频光谱，所用的仪器分别是高分辨傅立叶变换光谱仪和高灵敏激光腔内吸收光谱仪。用局域模模型和包含达林－丹尼生共振的简正模模型，归属了SiH伸缩振动的基频和泛频，振动量子数的改变△VSiH=1, 2, 3, 4 and 6。通过对实验能级的非线性拟合，得到SiH伸缩振动的谐振频率ωm、非谐性常数χm、键间耦合系数λ、莫尔斯振子参数 De、α 和相互作用力常数 。实验发现，随着振动能量的增加，振动簇（manifold，两个SiH键的伸缩振动量子数m+n=常数 ）中能量最低的两个能级的间距逐渐减小。当△VSiH≥4时，在实验误差范围内这两个最低的振动态能级简并。这种简并的能级结构类似双原子莫尔斯振子，符合Birge-Sponer 关系。双原子莫尔斯振子直接描述了H2SiCl2分子中SiH 的高泛频伸缩振动，表明在高振动情况下振动能量已经集中到单个SiH键上。     

Reaction products from a discharge of N2 and H2S: The microwave spectrum of NH2SH

Thiohydroxylamine has been identified as one of the reaction products from the discharge reaction of N₂ + H₂S. Both cis and trans conformers have been observed. The rotational spectra have been studied from 56 to 170 GHz for the normal species and several deuterated isotopic species of each conformer. The electric dipole moments of both conformers have been determined. A number of the transitions of the cis conformer exhibit splittings due to the nuclear quadrupole moment of the ¹⁴N nucleus. A least squares fit of the frequency splittings have led to an analysis of the eQq values. Ab initio calculations using a 4-31G basis set both with and without polarization functions have been carried out to aid in the analysis and to provide a final structural comparison with the microwave results.     

Centrifugal distortion analysis of pure rotational spectra of H216O,H217O,and H218O

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.