In this chapter the physical aspects of the global optimization of the geometry of atomic clusters are elucidated. In particular, I examine the structural principles that determine the nature of the lowest-energy structure, the physical reasons why some clusters are especially difficult to optimize and how the basin-hopping transformation of the potential energy surface enables these difficult ...

The photodynamics of bacteriorhodopsin were studied by transient absorption and gain measurements after excitation with femtosecond pulses at 620 nm. With probing pulses at longer wavelengths (A> 770 nm) the previously reported formation of the J intermediate (with a time constant of 500f 100 fs) was confirmed. With probing pulses around 700 nm, a faster process with a relaxation time of 200 rt...

The infrared photodissociation spectrum of the degenerate asymmetric CH stretch (n3) vibration of the CH3 –He ionic complex has been recorded. The rotational structure and vibrational frequency of the observed transition are consistent with a p-bonded C3v cluster geometry where the He ligand is attached to the 2pz orbital of the central C atom of CH3 1 . The intermolecular bond in the ground vi...

The high resolution absorption spectrum of monodeuterated water, HDO, has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) in the 12145–13160 cm 1 region. The achieved sensitivity (noise equivalent absorption on the order of amin 10 9 cm ) allowed detecting transitions with line strengths as weak as 10 27 cm/molecule which is about 50 times lower than the weakest line intensit...

The H, system has excited much mterest both theoretically [l] and experimentally [2]. In particular It has been used to study elastic, inelastic and reacttve scattermg. The H3 molecule has been observed in an excited Rydberg state [3], a Bndtng confirmed by ab initio calculation [4,5], but as yet we know of no experimental evidence for it in its electronrc ground state. The ground-state potenti...

The nuclear Franck-Condon factor for the photodetachment processes H(D)2F-+h~+H (D)2+Fte-, H(D)FtH(D) tefor J=O has been calculated using the S-matrix Kohn variational method for reactive scattering on the T5a potential energy surface. The positions of peaks in the spectra of our theoretical calculations are in excellent agreement with those found in the recent experiment of Weaver and Neumark....

The low-temperature rotational (de-) excitation of C3 (X 1 g ) by collisions with He ( S ) is studied using an ab initio potential energy surface (PES). This PES has been calculated using the singleand double-excitation coupledcluster approach with noniterative perturbational treatment of triple excitations [CCSD(T)] and the augmented correlation-consistent triplebasis set (aug-cc-pVTZ) with bo...

Molecular reaction dynamics in the adiabatic representation is complicated by the existence of conical intersections and the associated geometric phase effect. The first-derivative coupling vector between the corresponding electronically adiabatic states can, in general, be decomposed into longitudinal ~removable! and transverse ~nonremovable! parts. At intersection geometries, the longitudinal...

We present cross sections for rotational, vibrational, and fine-structure transitions in He–CaH(S) collisions at cold and ultracold temperatures calculated using the ab initio potential energy surface reported in the preceding paper. Rotational quenching is fast, vibrational quenching is slow. The spin-rotational interaction, although small and having no influence at temperatures above 10 K, ch...

in this work, the (100) surface of au and pts face centered cubic lattice, has been simulated in monte-carlo method, using a 486-dx2 computer. the potential equation that was used for the interaction among atoms in the metal surfaces is called sutton and chen potential. this potential is introduced for the interaction of floating nuclei in the electron sea, and attractive term is a many body po...