The Kinetics of the Recombination of Methyl Radicals and Iodine Atoms.

Marcus, R. A.; Rice, O. K.

doi:10.1021/j150489a013

Cited by 671 publications

(325 citation statements)

References 7 publications

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“…Rice-Ramsperger-Kassel-Marcus (RRKM) theory [1][2][3], derived from classical mechanics [3][4][5], is a limiting model for the dynamics of unimolecular decomposition. It assumes that the classical dynamics is ergodic on the time-scale of the unimolecular reaction so that a microcanonical ensemble of states is maintained for the molecules as they decompose [5].…”

Section: Introductionmentioning

confidence: 99%

Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br

Paranjothy

Sun

Paul

et al. 2013

Zeitschrift Für Physikalische Chemie

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Chemical dynamics simulations, based on both an analytic potential energy surface (PES) and direct dynamics, were used to investigate the intrinsic non-RRKM dynamics of the Cl products were fit with multi-exponential functions. The intrinsic non-RRKM dynamics is more pronounced for the simulations with the analytic PES than by direct dynamics, with the populations for the former and latter primarily represented by tri-and bi-exponential functions, respectively. For the analytic PES and direct dynamics simulations, the intrinsic non-RRKM dynamics is more important for the isomerization pathway to form ClCH 3 -Br − than for dissociation to Cl − + CH 3 Br. Since the decomposition probability of Cl − -CH 3 Br is non-exponential, the Cl − -CH 3 Br unimolecular rate constant depends on pressure, with both high and low pressure limits. The high pressure limit is the RRKM rate constant and for the simulations with the analytic PES the rate constant decreased by a factor of 3.0, 5.6, and 4.3 in going from the high to low pressure limit for total energies of 40, 60, and 80 kcal/mol. For the direct dynamics simulations these respective factors are 2.4, 1.4, and 1.2. A separable phase space model with intermolecular and intramolecular complexes describes some of the simulation results, but overall models advanced for intrinsic non-RRKM dynamics give incomplete representations of the intermediate and product populations vs. time determined from the simulations.

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Section: Introductionmentioning

confidence: 99%

Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br

Paranjothy

Sun

Paul

et al. 2013

Zeitschrift Für Physikalische Chemie

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“…4,5 Recent experimental and theoretical reviews [6][7][8][9] have demonstrated the importance of understanding the nature of intramolecular vibrational energy redistribution ͑IVR͒ in fields such as chemical dynamics and laser selective chemistry. Recent frequency domain experiments [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] have shown the efficacy of eigenstate resolved spectroscopy as a tool for the exploration of IVR behavior at ''long'' times.…”

Section: Introductionmentioning

confidence: 99%

A sub-Doppler resolution double resonance molecular beam infrared spectrometer operating at chemically relevant energies (∼2 eV)

Srivastava

Conjusteau

Mabuchi

et al. 2000

Review of Scientific Instruments

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A molecular beam spectrometer capable of achieving sub-Doppler resolution at 2 eV ͑ϳ18 000 cm Ϫ1 ) of vibrational excitation is described and its performance demonstrated using the CH stretch chromophore of HCN. Two high finesse resonant power-buildup cavities are used to excite the molecules using a sequential double resonance technique. A vϭ0→2 transition is first saturated using a 1.5 m color center laser, whereupon a fraction of the molecules is further excited to the vϭ6 level using an amplitude modulated Ti:Al 2 O 3 laser. The energy absorbed by the molecules is detected downstream of both excitation points by a cryogenically cooled bolometer using phase sensitive detection. A resolution of approximately 15 MHz ͑i.e., three parts in 10 8 ) is demonstrated by recording a rotational line in the vϭ6 manifold of HCN. Scan speeds of up to several cm Ϫ1 /h were obtained, with signal-to-noise ratios in excess of 100. The high signal-to-noise ratio and a dynamic range of 6ϫ10 4 means that future experiments to study statistical intramolecular vibrational energy redistribution in small molecules and unimolecular isomerizations can be attempted. We would also like to point out that, with improved metrology in laser wavelengths, this instrument can also be used to provide improved secondary frequency standards based upon the rovibrational spectra of molecules.

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“…In this way, analytic formulas for the density of states of collections of classical oscillators and rotors can be derived and have been the staple in unimolecular rate theory for many years. [32][33][34][35] The quantum mechanical trace in Eq. ͑1͒ is most readily carried out for separable Hamiltonians.…”

Section: Introductionmentioning

confidence: 99%

On the calculation of absolute spectral densities

Smith

Jeffrey

1996

The Journal of Chemical Physics

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On the relation of protein dynamics and exciton relaxation in pigment-protein complexes: An estimation of the spectral density and a theory for the calculation of optical spectra J. Chem. Phys. 116, 9997 (2002) A new method of calculating the absolute spectral density of a Hamiltonian operator is derived and discussed. The spectral density is expressed as the solution of an integral equation in which the kernel is a renormalized one-sided energy correlation function of the full microcanonical density operator and a microcanonical density operator for a reference Hamiltonian. The integral operator associated with this equation transforms a known spectral density function for the reference Hamiltonian into the spectral density of the full Hamiltonian. The integral equation, by virtue of its formulation in energy space, is inherently one-dimensional and offers no storage difficulties, and the elements of its kernel may be computed by applying the Lanczos algorithm to randomly selected eigenfunctions of the reference Hamiltonian. This spectral density correlation method offers a number of advantages over variational methods. In particular, it has the potential for overcoming the hitherto largely insurmountable problem of tracing over a multidimensional Hilbert space in order to compute the spectral density of a nonseparable molecular Hamiltonian.

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The Kinetics of the Recombination of Methyl Radicals and Iodine Atoms.

Cited by 671 publications

References 7 publications

Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br

Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br

A sub-Doppler resolution double resonance molecular beam infrared spectrometer operating at chemically relevant energies (∼2 eV)

On the calculation of absolute spectral densities

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