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Ng Pack G, Rotondaro MC, Shah PP, Mandal A, Erramilli S, Ziegler LD. Two-dimensional infrared spectroscopy from the gas to liquid phase: density dependent J-scrambling, vibrational relaxation, and the onset of liquid character. Phys Chem Chem Phys 2019; 21:21249-21261. [PMID: 31538165 DOI: 10.1039/c9cp04101j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast 2DIR spectra and pump-probe responses of the N2O ν3 asymmetric stretch in SF6 as a function of density from the gas to supercritical phase and liquid are reported. 2DIR spectra unequivocally reveal free rotor character at all densities studied in the gas and supercritical region. Analysis of the 2DIR spectra determines that J-scrambling or rotational relaxation in N2O is highly efficient, occurring in ∼1.5 to ∼2 collisions with SF6 at all non-liquid densities. In contrast, N2O ν3 vibrational energy relaxation requires ∼15 collisions, and complete vibrational equilibrium occurs on the ∼ns scale at all densities. An independent binary collision model is sufficient to describe these supercritical state point dynamics. The N2O ν3 in liquid SF6 2DIR spectrum shows no evidence of free rotor character or spectral diffusion. Using these 2DIR results, hindered rotor or liquid-like character is found in gas and all supercritical solutions for SF6 densities ≥ρ* = 0.3, and increases with SF6 density. 2DIR spectral analysis offers direct time domain evidence of critical slowing for SF6 solutions closest to the critical point density. Applications of 2DIR to other high density and supercritical solution dynamics and descriptions are discussed.
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Affiliation(s)
- Greg Ng Pack
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Matthew C Rotondaro
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Parth P Shah
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Aritra Mandal
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
| | - Shyamsunder Erramilli
- Photonics Center, Boston University, Boston, MA 02215, USA and Department of Physics, Boston University, Boston, MA 02215, USA
| | - L D Ziegler
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
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Tran H, Li G, Ebert V, Hartmann JM. Super- and sub-Lorentzian effects in the Ar-broadened line wings of HCl gas. J Chem Phys 2017; 146:194305. [PMID: 28527465 DOI: 10.1063/1.4983397] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using previously recorded spectra of HCl diluted in Ar gas at room temperature for several pressure conditions, we show that the absorptions in between successive P and R transitions are significantly different from those predicted using purely Lorentzian line shapes. Direct theoretical predictions of the spectra are also made using requantized classical molecular dynamics simulations and an input HCl-Ar interaction potential. They provide the time evolution of the dipole auto-correlation function (DAF) whose Fourier-Laplace transform yields the absorption spectrum. These calculations very well reproduce the observed super-Lorentzian behavior in the troughs between the intense lines in the central part of the band and the tendency of absorption to become sub-Lorentzian in the band wings between high J lines. The analysis shows that the former behavior is essentially due to incomplete collisions which govern the DAF at very short times. In addition, the increasing influence of line-mixing when going away from the band center explains the tendency of absorption to become more and more sub-Lorentzian in the wings.
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Affiliation(s)
- Ha Tran
- Laboratoire de Météorologie Dynamique, IPSL, CNRS, Sorbonne Universités, UPMC University Paris 06, 75252 Paris, France
| | - Gang Li
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
| | - Volker Ebert
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
| | - Jean-Michel Hartmann
- Laboratoire de Météorologie Dynamque, IPSL, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France
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Padilla A, Pérez J. Mixed classical quantum dynamical simulation of mid-infrared Q branch of HCl diluted in Ar. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2014.04.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Tran H, Domenech JL. Spectral shapes of Ar-broadened HCl lines in the fundamental band by classical molecular dynamics simulations and comparison with experiments. J Chem Phys 2014; 141:064313. [PMID: 25134577 DOI: 10.1063/1.4892590] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spectral shapes of isolated lines of HCl perturbed by Ar are investigated for the first time using classical molecular dynamics simulations (CMDS). Using reliable intermolecular potentials taken from the literature, these CMDS provide the time evolution of the auto-correlation function of the dipole moment, whose Fourier-Laplace transform leads to the absorption spectrum. In order to test these calculations, room temperature spectra of various lines in the fundamental band of HCl diluted in Ar are measured, in a large pressure range, with a difference-frequency laser spectrometer. Comparisons between measured and calculated spectra show that the CMDS are able to predict the large Dicke narrowing effect on the shape of HCl lines and to satisfactorily reproduce the shapes of HCl spectra at different pressures and for various rotational quantum numbers.
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Affiliation(s)
- H Tran
- Laboratoire Interuniversitaire des Systèmes Atmosphériques, UMR CNRS 7583, Université Paris Est Créteil, Université Paris Diderot, Institut Pierre-Simon Laplace, 94010 Créteil Cedex, France
| | - J-L Domenech
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, (IEM-CSIC), Serrano 123, 28006 Madrid, Spain
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Padilla A, Pérez J. Non-Markovian near-infrared Q branch of HCl diluted in liquid Ar. J Chem Phys 2013; 139:084505. [DOI: 10.1063/1.4818993] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Padilla A, Pérez J, Herrebout W, Van der Veken B, Bulanin M. A simulation study of the vibration–rotational spectra of HCl diluted in Ar: Rotational dynamics and the origin of the Q-branch. J Mol Struct 2010. [DOI: 10.1016/j.molstruc.2009.09.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cwiklik L, Devlin JP. Hindering of rotational motion of guest molecules in the Type I clathrate hydrate. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.06.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Medina A, Roco JMM, Hernández AC, Velasco S. Dynamical characterization of rotationally hindered species in liquids. J Chem Phys 2005; 123:234509. [PMID: 16392933 DOI: 10.1063/1.2137699] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The rotational dynamics of HCl in liquid Ar has been studied by means of molecular-dynamics simulations. We calculate the lifetimes of weakly bound HCl-Ar dimers induced by the anisotropic pair interaction. It is shown that, although lifetimes are small with respect to the reorientational decorrelation, the time interval between the breaking down and formation of the next dimer is negligibly small. Thus, with respect to the rotational dynamics of the probe, the effect is similar to that and eventually would cause a time-stable complex. This provokes a peculiar hindered rotation of the diatomic in the liquid which is macroscopically embodied in the infrared spectrum of the solution as a Q-branch nonexistent otherwise.
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Affiliation(s)
- A Medina
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain.
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Pérez J, Padilla A, Herrebout WA, Van der Veken BJ, Hernández AC, Bulanin MO. Experimental analysis and modified rotor description of the infrared fundamental band of HCl in Ar, Kr, and Xe solutions. J Chem Phys 2005; 122:194507. [PMID: 16161597 DOI: 10.1063/1.1902925] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report an experimental study of the rotovibrational fundamental PQR-band shapes in the IR absorption spectra of HCl dissolved in condensed rare gases in a wide range of temperatures. The effective vibrational frequencies are determined from analysis of the fine rotational structure partially resolved in the band wings. The central Q-branch components appear redshifted with respect to the effective vibrational frequencies, their shifts in different solvents found to match the HCl stretching mode shifts in binary Rg...HCl van der Waals heterodimers. Theoretical quasi-free rotor and modified rotor models are applied to describe evolution of the band profiles at changing thermodynamic conditions. Both models are shown to reproduce equally well the observed spectral density distributions in the band wings. However, the modified rotor formalism that accounts for depopulation of the lower-energy rotational solute states provides better agreement with the experiment in the range of the P- and R-branch maxima. We surmise that the Q branches separated from the measured spectral profiles are formed by transitions between rotationally hindered states of diatomic molecules coupled to the solvent by the local anisotropy of the interaction potential.
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Affiliation(s)
- J Pérez
- Departamento de Física Fundamental y Experimental Electrónica y Sistemas, Universidad de La Laguna, 38204 Tenerife, Spain.
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