Energy transfer rotation-translation

A brief review is presented of theoretical and computational studies of energy transfer among translational, rotational, vibrational, and electronic degrees of freedom in molecular systems. 

Wang Z S, Darling G R and Holloway S 2000 Translation-to-rotational energy transfer in seattering of H2 moleeules from Cu(111) surfaees Surf. Sc/. 458 63... 

Michaels C A, Lin Z, Mullin A S, Tapalian H C and Flynn G W 1997 Translational and rotational excitation of the C02(00°0) vibrationless state in the collisional quenching of highly vibrationally excited perfluorobenzene evidence for impulsive collisions accompanied by large energy transfers J. Chem. Phys. 106 7055-71... 

Kreutz T G and Flynn G W 1990 Analysis of translational, rotational, and vibrational energy transfer in collisions between COj and hot hydrogen atoms the three dimensional breathing ellipse model J. Chem. Phys. 93 452-65... 

A molecule vibrationally excited by absorption of a laser photon can convert its excitation energy into translational (F - T transfer), rotational (F-> i ), vibrational (V- F) or even electronic energy (F- ) of the collision partners. 

Energy transfer from molecules to the lattice are significantly more complicated because translational energy may simultaneously be transferred to molecular coordinates, e.g. rotation. /, as well as the lattice. Even for weak molecule-surface interactions, there is still strong anisotropy in the repulsive part of the PES, which causes strong translational-rotational conversion, En J. Because of the competition for En by both E and. /, an anti-correlation is observed between energy... 

Energy transfer occurring in nonreactive neutral-neutral collisions is a very active field of investigation.230 Important contributions to the understanding of collisional energy-transfer processes have also resulted from various studies of nonreactive ion-neutral collisions. The modes of energy transfer that have been investigated for the latter interactions include vibrational to relative translational (V-T), vibrational to vibrational (V-V), translational to vibrational (T-V), translational to rotational (T-R), vibrational to rotational (V-R), translational to electronic (T-E), and electronic to translational (E-T). 

Energy Transfer—(Excitation transfer).— As used in photochemistry the term is nonspecific and refers to any transfer of energy from an excited molecule to other species. The energy acceptor may itself be promoted to an excited electronic state or the electronic energy may be donated to a host system as vibrational, rotational or translational energy. The term is used to describe variously overall processes which may involve two or more steps (e.g., internal conversion followed by transfer of vibrational energy) and the individual steps in which the energy passes from one molecule to another (or others). 

The photofragmentation that occurs as a consequence of absorption of a photon is frequently viewed as a "half-collision" process (16)- The photon absorption prepares the molecule in assorted rovibrational states of an excited electronic pes and is followed by the half-collision event in which translational, vibrational, and rotational energy transfer may occur. It is the prediction of the corresponding product energy distributions and their correlation to features of the excited pes that is a major goal of theoretical efforts. In this section we summarize some of the quantum dynamical approaches that have been developed for polyatomic photodissociation. For ease of presentation we limit consideration to triatomic molecules and, further, follow in part the presentation of Heather and Light (17). 

First, collisional relaxation of rotation is fast. One to ten collisions are sufficient for rotation-translation energy transfer. At 1 torr at least one collision per microsecond will occur for both 02 and HC1. In contrast, rotational relaxation by radiation, when allowed, is very slow, of the order of 102 seconds. The absence of... 

Considering the four types of energy, translational, rotational, vibrational and electronic, it is convenient to classify ten types of molecular energy transfer. In some, the type of energy is preserved, for example the E-E process which produces population inversion in the He/Ne laser8... 

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