Foto del docente

Elisabetta Canè

Assistant professor

Department of Industrial Chemistry "Toso Montanari"

Academic discipline: CHIM/02 Physical Chemistry

Research

Keywords: Local Mode Model high resolution infrared spectroscopy overtone IR bands analysis State energies of symmetric rotors Anharmonic Resonance equilibrium structure ro-vibration band analysis

My recent scientific activity has been devoted to research in the field of the molecular spectroscopy on the following subjects

  1. Rovibrational analysis of the fundamental, overtone and combination bands of perchloryl fluoride observed in the high resolution infrared spectra of the pure isotopic samples of F35Cl16O3, F37Cl6O3, F35Cl18O3 and F37Cl18O3 recorded from 450 to 2200 cm-1. Determination of the molecular constants in the analysed states and of the anharmonic or vibro-rotational interactions constants effective between those states.
  2. Determination of the anhamonicity constants xij of the perchloryl fluoride from the combination of the band origins and evaluation of the rotation vibration interaction parameters from the rotational constants in the vibrational excited states. Determination of the equilibrium geometry of FClO3 from the equilibrium rotational constants.
  3. Calculation of the ab initio anharmonic force field of FClO3 and comparison of the calculated fundamental frequencies, of the anharmonicity constants and of the vibration rotation interaction constants with the experimental corresponding ones.
  4. Calculation of the ab initio anharmonic force field of naphthalene-h8 and naphthalene-d8 with the DFT method, using the B97-1 functional and TZ2P basis set. The calculated frequencies of the fundamental modes of vibration are compared with the experimental counterparts, to assign the vibration spectra of these molecules.
  5. Calculation of the ab initio anharmonic force field of 1,3-cyclepentadienes with the DFT method, using the B97-1 functional and TZ2p basis set. The calculated frequencies of the fundamental modes of vibration are compared to the experimental counterparts, to assign the vibration spectra of C5H6, C5D6, C5H5D and C5HD5.
  6. Analysis of the 3nu1 band system spectra of cyanoacetylene recorded at high resolution with the FT and ICLAS VECSEL techniques. Determination of the molecular constants of the observed bands  in this system and evaluation of the nature of the lower and upper states of the observed transitions.
  7. Vibro-rotational analysis of the high resolution infrared bands of acetylene and its isotopic derivatives recorded from the far-infrared to the near infrared, to characterise the states involved in the transitions and to derive the molecular constants of the various isotopic species in the excited states.
  8. High resolution infrared study of the first and second stretching overtone systems of SbD3. The aim is to characterise the analysed excited states form a spectroscopic point of view, i.e. to determine the energies of the rotational levels, the band origins the molecular constants and the interaction parameters of those excited states. The local mode model is used to describe the behaviour of the Sb-D stretching highly excited states also in comparison to the Sb-H ones.
  9. High resolution infrared study of the ground state, of the nu1 fundamental, and of the first overtone of nu1 of the asymmetric rotor SbHD2. The aim is to characterize the analysed states and to test the applicability of the extended local mode theory to the description of the overtone state.
  10. The high resolution spectrum of diacetylene from 500 to 1000 cm-1 has been recorded and analysed. The nu8 fundamental, the n7+n9 combination, the nu3-nu9 difference band and the nu8+nu9-nu9 and nu7 +2nu9-nu9 hot bands have been assigned and rovibrational analysed. The anharminic resonance effective between the v3 =1 , v8=v9=1 and V7=2 states have been considered in the model Hamiltonian.  Very precise spectroscopic parameters of the excite states have been obtained.
  11. The infrared spectrum of the ammonia isotopologue 15ND3 has been investigated by high resolution Fourier transform spectroscopy in the region from 450 to 1600 cm-1. In total, 2217 transitions involving the (s) and (a) inversion-rotation-vibration levels have been identified and assigned to the n2 and n4 bending fundamentals. The assigned transitions have been fitted simultaneously using an inversion-rotation-vibration effective Hamiltonian which includes all symmetry allowed interactions between and within the excited state levels. The adopted model has been successful in rationalizing the complicated energy level pattern. Accurate values for the vibration and rotation spectroscopic constants, including 11 interaction coefficients, have been obtained for both inversion levels of the v2 = 1 and v4 = 1 states. The standard deviation of the fit, 0.00071 cm-1, is about two times the estimated measurement precision.

  12. The 2nu1 (A1), Si-H stretching overtone band of HSiD3 has been recorded at a resolution of ca. 0.009 cm-1 between 4200 and 4400 cm-1. About 790 ro-vibration transitions of the H28SiD3 isotopologue have been assigned, with J ' up to 24 and K up to 21. The spectrum evidences the existence of several perturbations. The assigned transitions have been analyzed either neglecting or including in the model A1/E Coriolis-type interactions between v1 = 2 and nearby dark states. The standard deviation of all the fits is, however, more than one order of magnitude larger than the estimated experimental precision and is independent of the adopted model.

  13. The FTIR spectra of CH2ClF (natural isotopic mixture) and CH237ClF (isotopically enriched sample) were investigated in the n5 and 2n6 region between 700 and 800 cm-1 at a resolution of 0.004 cm-1. The nu5 and 2nu6 vibrations of A' symmetry give rise to a/b hybrid bands with a very predominant a-type component. Due to the proximity of their band origins, the v5 = 1 and v6 = 2 levels perturb each other by Fermi and Coriolis resonances. The interaction mechanisms, previously investigated in the rotational spectra of CH235ClF, were extended to the less abundant isotopic species CH237ClF and to higher J and Ka values in the main isotopologue. The spectral analysis resulted in the identification of 4188  and 5392 transitions for CH235ClF and CH237ClF, respectively. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the Ir representation and perturbation operators. Excited state parameters, band origins and coupling terms for the nu5/2nu6 dyad of both isotopologues were determined.

      14.   Diacetylene, C4H2, has been identified in several astronomical environments through its infrared spectrum. In contrast, monodeuterated diacetylene (DC4H) has not been detected in space so far owing to the low isotopic abundance of deuterated species but also to the rather poor laboratory spectroscopic characterisation of this molecule. Aims. The aim of this work is to provide accurate spectroscopic parameters for DC4H to achieve reliable predictions for both its spectra at millimetre and infrared wavelengths. Methods. We studied the rotational spectrum of DC4H in the range 85-615 GHz by millimetre-wave spectroscopy and the infrared spectrum below 1000 cm(-1) by high-resolution, Fourier-transform spectroscopy. Several pure rotational transitions were recorded in the ground state and in excited vibrational bending states. The three fundamental bands v(6), v(7), and v(8) have been identified and assigned in the infrared spectrum. Results. The rotational transitions were analysed together with the infrared data in a global fit that produces very accurate rovibrational parameters. The observed frequencies and wavenumbers are reported to provide precise guidance for astronomical searches.

15.The infrared spectrum of the perdeuterated acetylene, 12C2D2, has been recorded from 900 cm−1 to 5500 cm−1 by Fourier transform spectroscopy at a resolution ranging between 0.004 and 0.009 cm−1. Ninety-two bands involving the ν1, ν2, and ν3 stretching modes, also associated with the ν4 and ν5 bending vibrations and 9 bands involving pure bending transitions have been observed and analysed. In total, 8345 transitions for the stretching-bending, and 862 for the pure bending modes have been assigned in the investigated spectral region. All the transitions relative to each stretching mode, i.e. the fundamental, its first overtone, and associated hot and combination bands involving bending states up to v 4 + v 5 = 2, were fitted simultaneously. The Hamiltonian adopted for the analysis is that appropriate to a linear molecule and includes vibration and rotation l-type interactions. The Darling−Dennison interaction between v 4 = 2 and v 5 = 2 levels associated with the various stretching states was also considered. The standard deviation for each global fit is smaller than 0.0006 cm−1, of the same order of magnitude of the measurement precision.

16. The high-resolution infrared spectrum of monodeuterated diacetylene has been recorded in the 4501100 cm(-1) spectral region by Fourier transform infrared spectroscopy. Seven new bands have been identified: the nu(3) fundamental (C-C stretch), and the nu(8) + nu(9), nu(7) + nu(8), 2 nu(7), 2 nu(8), nu(8) + nu(9) - nu(9), and nu(6) + nu(9) - nu(9) combination, overtone, and hot bands. The assigned transitions, together with those previously reported for the fundamental bands [F. Tamassia, L. Bizzocchi, C. Degli Esposti, L. Dore, M. Di Lauro, L. Fusina, M. Villa, and E. Cane, Astron. Astrophys. 549, A38 (2013)], form a comprehensive data set which comprises more than 2500 ro-vibrational transitions, and involves all singly and most doubly excited vibrational states of DC4H lying below 1000 cm(-1). Rotational and vibrational l-type resonance effects among the sub-levels of excited bending states were considered in the analysis, which also included a careful treatment of the various anharmonic interactions coupling many vibrational states lying above 600 cm(-1). Reliable and unambiguous spectroscopic parameters were obtained for each investigated state, including the rotational and centrifugal distortion constants B-nu and D-nu, the l-type doubling parameter q(t), the anharmonicity constants x(L)(89), x(L)(69), and the vibrational l-type terms r(89), r(69) for the upsilon(8) = upsilon(9) = 1 and upsilon(6) = upsilon(9) = 1 bend-bend combination states. (C) 2013 AIP Publishing LLC.

17. Infrared spectra of deuterated monofluoroacetylene, DCCF, have been recorded in the region between 320 and 850 cm-1 at an effective resolution ranging from 0.0024 to 0.0031 cm-1. In total, 6650 rotation vibration transitions were assigned to 37 bands involving the bending states with v4 + v5 and |l4 + l5|, respectively, up to 3, allowing the characterization of the ground state and of 18 vibrationally excited states. The n5 bending fundamental has been studied for the first time. In addition, the difference band n3 ¬ n4 has been detected and analyzed. All the assigned transitions have been fitted simultaneously by adopting a model Hamiltonian which takes into account the vibration and rotation l-type resonances. Rotational transitions in the ground and in bending excited states reported in the literature have been included in the global analysis. The set of 57 derived spectroscopic parameters reproduces 6130 infrared and 90 microwave and millimetre-wave transitions satisfactorily with root mean square values of 5.3 ×10-4 cm-1, and 77 kHz, respectively.

18.The high-resolution infrared spectrum of deuterated acetylene containing one 13C atom, 13C12CD2, has been recorded by Fourier transform spectroscopy in the range 450 - 1700 cm-1. The n4 and n5 bending fundamental bands and a number of overtone, combination and hot bands were identified. In total, 3210 rotation vibration transitions were assigned to 27 bands involving bending states with both v4 + v5 and |l4 + l5| up to 3. The ground state and 13 vibrationally excited states were characterized, i.e. all the l-vibrational components of the excited bending manifolds with v4 + v5 up to 2,  ( ),  ( ), and  (P and F). Two simultaneous least-squares fits of all assigned transitions have been performed, one considering transitions with v4 + v5 up to 2, the other adding the transitions with v4 + v5 = 3. The model Hamiltonian adopted for the analysis takes into account the usual vibration and rotation l-type resonances within each vibrational manifold and the Darling-Dennison anharmonic resonance between  and  and between  and . Two sets of 33 and 42, respectively, spectroscopic parameters were derived. They reproduce 1512 and 2450 assigned transitions with root mean square values of 3.5 × 10-4 and 3.9 × 10-4 cm-1, respectively. The transitions of four hot bands reaching the  ( ) state were fitted simultaneously to the effective upper state parameters.

19. The n4 fundamental band of CF379Br and CF381Br, present in natural isotopic abundance, was investigated in the 8.3 mm region by high resolution infrared spectroscopic techniques. Tuneable diode laser spectra were recorded in the ranges 1202.5-1205.0 cm-1, 1208.0-1210.1 cm-1 and 1212.5-1214.5 cm-1 . The tuneable diode laser spectra were obtained at the reduced temperature of 200 K and in a free-jet expansion. The latter technique was used to reduce spectral congestion, achieving a rotational temperature of about 50 K, with a resolution up to 0.0008 cm-1. A Fourier transform infrared spectrum covering the entire spectral region of the n4 band, between 1190 and 1220 cm-1, was recorded at 298 K with a resolution of 0.004 cm-1. The experimental wavenumbers from the different spectroscopic techniques were combined to accomplish the complete ro-vibrational analysis of n4. In total, 4651 transitions were assigned to CF379Br, 4047 to CF381Br, with ; of these, 3171 for CF379Br and 2755 for CF381Br are from diode laser measurements. The data of each isotopologue were analysed using the model Hamiltonian for a degenerate vibrational state of a molecule of C3v symmetry. The n4 band of both isotopologues resulted essentially unperturbed but the  l-resonance was found to be active within the v4 = 1 state. Precise values of the vibrational energy and of the ro-vibrational parameters of v4 = 1 for CF379Br and CF381Br were obtained. The bromine isotopic splitting amounts to 6.9 ´ 10-3 cm-1. In addition, the equilibrium geometry and the harmonic force field were calculated ab initio using the large-size basis set def2-QZVP in conjunction to the PBE0 functional.

20. The infrared spectrum of fully deuterated diacetylene below 1000 cm−1
L. Bizzocchi, F. Tamassia, C. Degli Esposti, L. Dore, M. Villa, and E. Canè
Abstract
Diacetylene (HC4H) is the simplest polyyne and has been the subject of several studies related
to technology, materials, supramolecular chemistry, non linear optics. It has been detected in the
space and in the atmosphere of Titan. Moreover, it is a model species to test sophisticated ab initio
calculations. In this paper we report the study of the infrared spectrum of the rare isotopologue
DC4D below 1000 cm−1. The experiment has been performed by high resolution Fourier transform
infrared spectroscopy. The 8 fundamental band, the 6 + 9, 7 + 8, and 6 + 8 combination
bands and the 8 +9 −9 hot band have been observed and analysed, providing a set of accurate
spectroscopic parameters. A global fit has also been performed in order to take into account the
anharmonic resonance between the v3 = 1 and the v8 = v9 = 1 states. The final results obtained
from the global fit show a good improvement in the spectroscopic parameters for both the upper
and lower states.

21.

High resolution infrared and Raman spectra of 13C12CD2: the CD stretching fundamentals and associated combination and hot bands

 G. Di Lonardo, L. Fusina, E. Canè, F. Tamassia, R. Z. Martínez and D. Bermejo

Infrared and Raman spectra of mono 13C fully deuterated acetylene, 13C12CD2, have been recorded and analysed to obtain detailed information on the CD stretching fundamentals n1 and n3 and associated combination, overtone and hot bands. Infrared spectra were recorded at a resolution ranging between 0.004 and 0.01 cm-1 in the region 1900 - 7800 cm-1. Sixty new bands involving the nu1 and nu3 C-D stretching modes, also associated with the nu4 and nu5 bending vibrations have been observed and analysed. In total, 5881 transitions have been assigned in the investigated spectral region. In addition, the Q-branch of the nu2 fundamental was recorded using inverse Raman spectroscopy, with an instrumental resolution of about 0.003 cm-1. The transitions relative to each stretching mode, i.e. the fundamental band, its first overtone, and associated hot and combination bands involving bending states with v4+v5 up to 2 were fitted simultaneously. The usual Hamiltonian appropriate to a linear molecule, including vibration and rotation l-type and the Darling-Dennison interaction between v4=2 and v5=2 levels associated with the stretching states, was adopted for the analysis. The standard deviation for each global fit is ≤ 0.0004 cm-1, of the same order of magnitude of the measurement precision. Slightly improved parameters for the bending and the nu2 manifold have been also determined. 

22. High resolution FTIR spectroscopy of HCFC-31 in the 950−1160 cm-1 region:rovibrational analysis and resonances in the ν4 , ν9 and ν5+ν6 bands of CH235ClF.

The FTIR spectrum of CH2ClF (natural isotopic mixture) was investigated in the ν4, ν9 and ν5+ν6 band region between 950 and 1160 cm-1 at the resolution of 0.004 cm-1. The ν4 and ν5+ν6 vibrations of A' symmetry give rise to a/b hybrid bands with a predominant a-type component. The ν9 vibration of A" symmetry, expected with a c type band contour, shows an intense Coriolis-induced parallel component (Ka = 0,Kc = 0) deriving from mixing with the v4 = 1 vibrational state. The high resolution spectra of ν9 and ν5+ν6 have been analyzed for the first time, while the assignments of the ν4 band, previously investigated, have been extended to higher J and Ka values in the b-type component. The spectral analysis resulted in the identification of 1508, 809 and 349 transitions for the ν4, ν9 and ν5+ν6 bands of CH235ClF, respectively. Besides the strong first-order a- and b-type Coriolis resonances between ν4 and ν9, the ν5+ν6 vibration was found to interact through a c-type Coriolis with the ν4 and 3ν6. High-order anharmonic resonance (Ka = ±2) between ν4 and ν5+ν6 was also established. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian
in the Ir representation and the relevant perturbation operators. The model employed includes five types of resonances within the tetrad ν4/ν9/ν5+ν6/3ν6. Α set of spectroscopic constants for ν4, ν9 and ν5+ν6 bands as well as parameters for the dark state 3ν6 and seven coupling terms have been determined. The simulations performed in different spectral regions satisfactorily reproduce the experimental data.

 



My reaseach activity has been devoted since 1990 up to now in the field of the high resolution molecular spectroscopy of gas phase samples, in the UV-VIS, in the infrared and in the microwave and millimeter wave regions.
The research in the infrared is mainly devoted to the determination of molecular ro-vibrational spectroscopic parameters from experimental rotational and ro-vibrational transitions.
The infrared spectra are recorded with a Bomem DA3.002 FTIR spectrometer, which can achieve a maximum resolution of 0.004 cm-1. A wide range of molecules, most of atmospheric and astrophysical interest, have been studied : C2H2,C4H2, PD3, SbD3,SiH3D, FClO3 (symmetric tops),  SbHD2, C2H4 and aza-aromatic compounds that can be classified as derivatives of purine and pyrimidine, (asymmetric tops). In addition, test-molecules which can be representative of some classes of compounds, i.e. acetylene and benzene and naphthalene, are studied to test theoretical models, like the local mode model, or different redustion of the rotational or rovibrational Hamiltonian. 
The study of the spectra of many different isotopomers of the acetylene, phophine, stibine, perchloryl fluoride and aromatic compounds like benzene, naphtalene, cyclopentadiene, anthracene and phenanthrene, provides extensive information for the determination of the anharmonic force field and molecular geometry. Sometimes, the IR spectra are complemented by data obtained with the Raman technique and are supported by ab initio calculations.
The analysis of experimental data is performed on the basis of sophisticated theoretical models and requires the implementation of adequate computer programs. It provides the energies of the vibrational levels and the rotational and distortion parameters.
The investigation of vibrationally excited states perturbed by ro-vibrational interactions of Fermi or Coriolis type is of great interest for the determination of the interaction parameters, which characterise the dynamics of molecular processes related to the energy transfer.

The reasearch in the UV-Visible region has been done by means of a concave grating spectrograph, with a working resolution of 0.05 cm-1, operating in the laboratory. The absorption spectra are recorded on plates and then transformed into digital files by means of a high-resolution scanner. The spectroscopic parameters of the electronic states involved in the transitions are determined from the analysis of the spectra and are used together with infrared data to derive the experimental anharmonicity constants.
From the rotational analysis of the microwave and millimeter wave spectra of the aza-aromatic molecules the following spectroscopic parameters have been derived: the molecular constants in the electronic ground state, the molecular geometry, the Stark coefficients and the dipole moments.