%e have developed a general perturbative theory which describes how coherent wall interactions afFect the NMR spectrum of nuclear-spin-polarized gases in containers of any shape. The important practical case of cylindrical containers with quadrupolar wall interactions has been worked out completely. The basic results are quite simple. The frequency shift and damping of the NMR spectrum depend o...

the hydrogen abstraction reaction by oh radical from ch2brch2br (r1) and ch₃chbr2 (r2) is investigated theoretically by semi-classical transition state theory. the stationary points for both reactions are located by using ωb97x-d and kmlyp density functional methods along with cc-pvtz basis. single-point energy calculations are performed at the qcisd(t) and ccsd(t) levels of theory with differe...

: 1h nmr spectra of a series of enaminones r-co-ch=c(nhch2ph)-r  [1, r=ch3; 2, r=c6h5; 3, r=cf3; 4, r=ch2ch2ch2; 5, r=ch2c(ch3)2ch2], were obtained in the presence of trifluoroacetic acid in cdcl3 or dmso-d6 at 28 °c. steric, solvent, electronic and hydrogen bonding effects on the rates of acid-catalyzed nh proton exchanges were investigated. rate constants were calculated by 1h nmr line shape ...

Using the standard, low pressure, discharge-flow technique, with resonance fluorescence in the vacuum ultraviolet to observe Cl atoms, rate constants have been determined for the reaction of Cl atoms with O3 at temperatures down to 184 K. The measured rate constants for 298184 K fit the Arrhenius expression: k(T) = (3.6 ± 0.7) × 10 exp(( 310 ± 50 K) / T) cm molecule s. The results extend the d...

Rate constants for the unimolecular decomposition of peptide monomer and dimer ions by thermal and surface-induced dissociation (SID) are measured and compared. Rate constants for thermal dissociation are measured in a heated wide-bore capillary flow reactor attached in front of the capillary leading into the mass spectrometer. Thermal decomposition of the leucine enkephalin ion (YGGFL)H+ is ob...

Rovibrational energy transfer of hydrogen fluoride in collisions with argon was investigated by using the coupled-states approximation to the quantum scattering problem. Empirically determined 3-D ab initio potential energy surfaces ~PES! for the interaction between hydrogen fluoride and argon are presented. Second-order Møller-Plesset perturbation theory ~MP2! was used to provide an initial ap...

Studies of Rydberg atom collision processes, especially those with small reaction rate constants, are frequently complicated by spurious background signals associated with photoionization by thermal blackbody radiation and with ionization resulting from collisions with background gas. Here we demonstrate that the magnitude and relative importance of the signals that result from these processes ...

The advent of gas lasers has caused considerable interest in energy-transfer mechanisms that would create or degrade a population inversion. In molecular gases, rotational energy transfer (RET) is by far the most probable collision process, being typically 1-2 orders of magnitude more likely than vibrational transfer and 2-3 orders of magnitude more likely than electronic energy transfer. We ha...

We compute ab initio cross sections for cold collisions of Rb atoms with OH radicals. We predict collision rate constants of order 10(-11) cm3/s at temperatures in the range 10-100 mK at which molecules have already been produced. However, we also find that in these collisions the molecules have a strong propensity for changing their internal state, which could make sympathetic cooling of OH in...

The kinetic rate constants of binding were estimated for four biochemically relevant molecular systems by a method that uses milestoning theory to combine Brownian dynamics simulations with more detailed molecular dynamics simulations. The rate constants found using this method agreed well with experimentally and theoretically obtained values. We predicted the association rate of a small charge...