Metastable and collision-induced decompositions of mass-selected {ROH} n {H 2 O}H + cluster ions (where R ≡ CH 3 -, CH 3 CH 2 -, CH 3 CH 2 CH 2 -, and (CH 3 ) 2 CH -) were observed to exhibit distinct size-dependent behavior. We observe that loss of a water molecule is dominant for n e 8, whereas loss of multiple ROH molecules is the favored decomposition channel for n g 9, resulting in the eventual formation of a stable {ROH} 9 -{H 2 O}H + cluster ion. We believe this is evidence for two distinct cluster geometries which explicitly depend on the number of ROH molecules present. That is, below a certain critical size the proton resides on the molecule with the highest proton affinity, the ROH. However, above that critical cluster size the proton will now preferentially reside on the water molecule, if there are sufficient alcohols to completely and symmetrically solvate the central H 3 O + . The structural implications of these results will be discussed in light of new theoretical calculations which have been performed on this system.
Molecular beam electric resonance spectroscopy has been done on the v=0 and v=1 states of hydrogen fluoride in external electric and magnetic fields. The v=1 state was populated using a color center laser. v=0, v=1, and equilibrium configuration results have been obtained for the HF dipole moment, fluorine and proton spin rotation interactions, fluorine and proton magnetic shielding anisotropies, both direct and indirect spin–spin interactions, rotational magnetic moment, and magnetic susceptibility. All of these properties can be extrapolated to v=2 with high accuracy and to higher states with reasonable confidence. First and second derivatives with respect to internuclear distance have also been obtained for several of these properties. Comparisons of HF and DF dipole moments indicate significant differences arising from Born–Oppenheimer breakdown.
Cyanoacetylene was studied using molecular beam electric resonance spectroscopy. Ground state results are μ=3.731 72 D, eQq=−4319.24 kHz, CN=0.976 kHz. Zero field spectra were observed for the three singly excited bending modes and Stark data were taken for the lower energy of two of these three states. Excited state results include ν7; μ=3.7225 D, eQqaa=−4302.0 kHz, eQ(qbb−qcc)=−28.8 kHz, CN(J=2)=1.47 kHz; ν6; μ=3.7263 D, eQqaa=−4369.7 kHz, eQ(qbb−qcc)=177.1 kHz, CB(J=2)=1.30 kHz; ν5; eQqaa=−4325.7, eQ(qbb−qcc)=96.8 kHz, CN(J=2)=1.33 kHz. l-doubling constants were also obtained for the degenerate vibrations.
Describing van der Waals Interaction in diatomic molecules with generalized gradient approximations: The role of the exchange functional Structure and properties of the argon-ozone van der Waals molecule Radio frequency spectroscopy and Stark effect measurements have been carried out on Ar·HCCH and Ar·DCCD produced in acetylene seeded argon beams. Because of the very small electric dipole moment, Il = 0.02697(3) D, only the 110-111 transition and low frequency pure Stark transitions were observed. Observations are only compartible with a T-shaped equilibrium structure with an Ar to acetylene distance of 3.25(I)A. Deuterium hyperfme data provide a 204.4(10) KHz value for eqQ of acetylene and arccos (v'
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