Vibrational*state populations, molecules

The knowledge of the internal-energy distribution is of equal interest for the practical applications indicated in the preceding paragraphs. First spectroscopic obervations of the IR emission from the molecule BC, which is related to the vibrational-state population, were reported by Karl and Polanyi13 on the system Hg + CO. These measurements were subsequently improved and extended.14-16 Recent time-resolved experiments with IR-laser absorption17- 18 and emission techniques19-21 yield more reliable results on the product-state distribution. 

M. Rodriguez, B.M. Garraway, K.-A. Suominen, Tailoring of vibrational state populations with light-induced potentials in molecules, Phys. Rev. A 62 (2000) 053413. 

The complexity of reactions in solution has already been described briefly. However, many unimolecular reactions have rates in solutions that are approximately equal to those in the gas phase. The population of the transition state depends on the number of critical vibrational states populated, which is a function of temperature rather than the environment of the reacting molecule. The localization of the required energy in a vibrational mode for a bond to be broken is often somewhat independent of the environment of the molecule. 

C3.3.4 DEDUCING ENERGY TRANSFER MECHANISMS FROM POPULATION AND VELOCITY DISTRIBUTIONS OF THE SCATTERED BATH MOLECULES ROTATIONAL STATE POPULATION DISTRIBUTIONS FOR VIBRATIONAL EXCITATION OF THE BATH... 

For most purposes only the Stokes-shifted Raman spectmm, which results from molecules in the ground electronic and vibrational states being excited, is measured and reported. Anti-Stokes spectra arise from molecules in vibrational excited states returning to the ground state. The relative intensities of the Stokes and anti-Stokes bands are proportional to the relative populations of the ground and excited vibrational states. These proportions are temperature-dependent and foUow a Boltzmann distribution. At room temperature, the anti-Stokes Stokes intensity ratio decreases by a factor of 10 with each 480 cm from the exciting frequency. Because of the weakness of the anti-Stokes spectmm (except at low frequency shift), the most important use of this spectmm is for optical temperature measurement (qv) using the Boltzmann distribution function. 

In this section, we focus our attention on applications of the CDF protocol to control of population transfer between vibrational levels of a nonrotating polyatomic molecule. The vibrational spectrum of a polyatomic molecule is rich, and if one wishes to transfer population between two states in a subset of selected states that is embedded in the complete manifold of molecular vibrational states, it is... 

The modification of the electronic potentials due to the interaction with the electric field of the laser pulse has another important aspect pertaining to molecules as the nuclear motion can be significantly altered in light-induced potentials. Experimental examples for modifying the course of reactions of neutral molecules after an initial excitation via altering the potential surfaces can be found in Refs 56, 57, where the amount of initial excitation on the molecular potential can be set via Rabi-type oscillations [58]. Nonresonant interaction with an excited vibrational wavepacket can in addition change the population of the vibrational states [59]. Note that this nonresonant Stark control acts on the timescale of the intensity envelope of an ultrashort laser pulse [60]. 

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