Michael C. L. Gerry

Noble gas–metal chemical bonding? The microwave spectra, structures, and hyperfine constants of Ar–CuX(X=F, Cl, Br)

The rotational spectra of the complexes Ar–CuF, Ar–CuCl, and Ar–CuBr have been observed in the frequency range 5–22 GHz using a pulsed-jet cavity Fourier transform microwave spectrometer. All the complexes are linear and rather rigid in the ground vibrational state, with the Ar–Cu stretching frequency estimated as ∼200 cm−1. Isotopic data have been used to calculate an r0 structure for Ar–CuF, while for Ar–CuCl and Ar–CuBr partial substitution structures have also been obtained. To reduce zero-point vibrational effects a double substitution method (rd) has also been employed to calculate the structures of Ar–CuCl and Ar–CuBr. The Ar–Cu distance has been found to be rather short and to range from 2.22 A in Ar–CuF to 2.30 A in Ar–CuBr. Ab initio calculations at the MP2 level of theory model the geometries and stretching frequencies well and predict an Ar–Cu bond energy in Ar–CuF of ∼47.3 kJ mol−1. Large changes in the Cu nuclear quadrupole coupling constant on complex formation show that extensive charge re...

The microwave spectra and structures of Ar–AgX (X=F,Cl,Br)

The rotational spectra of the complexes Ar–AgF, Ar–AgCl, and Ar–AgBr have been observed in the frequency range 6–20 GHz using a pulsed jet cavity Fourier transform microwave spectrometer. All the complexes are linear and rather rigid in the ground vibrational state, with the Ar–Ag stretching frequency estimated as ∼140 cm−1. Isotopic data have been used to calculate an r0 structure for Ar–AgF, while for Ar–AgCl and Ar–AgBr partial substitution structures have also been obtained. To reduce zero-point vibrational effects a double substitution method (rd) was employed to calculate the structures of Ar–AgCl and Ar–AgBr. The Ar–Ag bond distance has been found to be rather short and to range from 2.56 A in Ar–AgF to 2.64 A in Ar–AgBr. Ab initio MP2 and density functional theory calculations for Ar–AgF and Ar–AgCl model the geometries and stretching frequency well, and predict an Ar–Ag bond energy in Ar–AgF of ∼23 kJ mol−1. These results indicate that the Ar–AgX complexes are more strongly bound than typical van...

The rotational spectrum of the isotopically substituted van der Waals complex ArOCS, obtained using a pulsed beam microwave Fourier transform spectrometer

Abstract A sensitive new pulsed beam cavity microwave Fourier transform spectrometer has been constructed. It has been used to measure for the first time the pure rotational spectra of the van der Waals complexes ArO 13 CS, Ar 18 OCS and Ar 17 OCS, and to measure further transitions of ArOC 34 S. Rotational and centrifugal distortion constants have been determined for all species, as well as 17 O quadrupole coupling constants in Ar 17 OCS. A harmonic force field has been obtained for the van der Walls motions, and has been used to reproduce the variations of distortion constants with isotopomer. Both substitution and ground state average structures have been evaluated. It is confirmed that the complex is a loose binding of Ar and OCS, with little change in the structural parameters of OCS from those of the free molecule.

Rotational spectrum, structure, and chlorine nuclear quadrupole coupling constants of the van der Waals complex Ar–Cl2

The pure rotational spectrum of the van der Waals complex Ar–Cl2 has been observed between 5 and 14 GHz using a Balle–Flygare type pulsed molecular beam microwave Fourier transform spectrometer. Ten a‐type rotational transitions of Ar–35Cl2, as well as five a‐type rotational transitions of the mixed isotopomer Ar–35Cl37Cl, have been assigned. The rotational constants and quartic centrifugal distortion constants have been determined. Unlike its isovalent linear isomer Ar–ClF, Ar–Cl2 has been found to be a T‐shaped complex. This confirms the result from electronic spectroscopy and is in accord with the atom–atom additive model. The distance from the Ar nucleus to the center of mass of the Cl2 subunit has been calculated to be 3.7190 A for Ar–35Cl2 and 3.7184 A for Ar–35Cl37Cl, respectively. The van der Waals stretch and bend force constants, as well as their corresponding harmonic vibrational frequencies, have been derived and compared with the theoretically predicted values. The nuclear hyperfine splitting...

Noble gas–metal chemical bonding: the microwave spectra, structures and hyperfine constants of Ar–AuF and Ar–AuBr

The rotational spectra of the complexes Ar–AuF and Ar–AuBr have been observed in the frequency range 7–22 GHz using a pulsed-jet cavity Fourier transform microwave spectrometer. Both complexes are linear and rather rigid in the ground vibrational state, with the Ar–Au stretching frequency estimated as ∽200 cm−1. Isotopic data have been used to calculate an r0 structure for Ar–AuBr while for Ar–AuF only an estimation of the r0 geometry could be made. Ab initio calculations at the MP2 level of theory model the geometries and stretching frequencies well and predict an Ar–Au bond energy in Ar–AuF of ∽60 kJ mol−1. The Au nuclear quadrupole coupling constant changes significantly on complex formation, indicating extensive charge arrangement. This in conjunction with the large dissociation energy and ab initio results show that the Ar–Au bonds in these complexes are weakly covalent in nature.

The microwave spectrum of the van der Waals complex ArN2

The microwave spectrum of the van der Waals complex ArN2 has been investigated. 14N quadrupole coupling constants, rotational and centrifugal distortion constants, structural parameters and an estimate of the dipole moment have been obtained. A value for the 14N quadrupole coupling constant for free nitrogen has been derived.

The torsion-rotation microwave spectrum of 12CH318OH and the structure of methanol

Abstract The microwave and millimeter wave spectrum of 12 CH 3 18 OH has been observed in the frequency region 7.9–200 GHz. Both a - and b -type transitions have been assigned and measured. This spectrum was analyzed using the method of Lees and Baker, and rotational constants, torsional constants, centrifugal distortion constants, the barrier to internal rotation and moments of inertia have been evaluated. The barrier has been found to be 374.91 ± 0.18 cm −1 , in good agreement with that of 12 CH 3 16 OH. The moments of inertia were combined with those of other isotopic species to give a full substitution structure. To assist searches for this molecule in interstellar space a table of predicted frequencies of astrophysically interesting transitions is presented.

The microwave rotational spectrum of the Ar–CO dimer

Pure rotational spectra of four different isotopomers of the dimer Ar–CO have been investigated between 8 and 18 GHz using a pulsed beam cavity Fourier transform spectrometer. The spectra confirm that the complex is a prolate near‐symmetric rotor with an essentially T‐shaped structure, and that it undergoes large amplitude zero‐point motion. It is shown that on the average the argon is closer to the oxygen than to the carbon. The transitions measured obey a‐type selection rules with ΔJ=+1, ΔKa=0, and ΔKc=+1. For 40Ar–12C16O, transitions have been observed for Ka=0 and 1 with lower state J values of 1, 2, and 3. For 40Ar–13C16O and 40Ar–13C18O, a similar series was measured, but only for Ka=0. For 40Ar–13C17O, the 17O quadrupole hyperfine pattern was resolved in the rotational transition JKaKc = 202–101. Determinations have been made for rotational and centrifugal distortion constants, as well as for the 17O quadrupole coupling constant χaa. Effective values have been obtained for the length of the line fr...

Microwave spectra and centrifugal distortion constants of formic acid containing 13C and 18O: Refinement of the harmonic force field and the molecular structure☆

Abstract Pure rotational spectra of H 13 COOH, HC 18 OOH, and HCO 18 OH have been measured in the frequency region 8–185 GHz. Analysis of the spectra has given improved rotational constants and quartic and sextic centrifugal distortion constants. The quartic distortion constants have been combined with previously published distortion constants of four other isotopic species, and with the vibrational wavenumbers of seven isotopic species, to produce a refined harmonic force field. An improved substitution structure and the ground state average structure have been obtained. Some unmeasured transition frequencies which may be of importance in radioastronomy are also presented.

Pure rotational spectra of the mixed rare gas van der Waals complexes Ne–Xe, Ar–Xe, and Kr–Xe

Pure rotational transitions in the vibrational ground states of various isotopomers of the heteronuclear rare gas dimers Ne–Xe, Ar–Xe, and Kr–Xe have been measured using a pulsed molecular beam cavity microwave Fourier transform spectrometer. Rotational and centrifugal distortion constants have been obtained, and have yielded estimates of the lengths of the van der Waals bonds and of their harmonic vibration frequencies. Effects due to nuclear quadrupole coupling have been observed in 131Xe‐containing complexes and have yielded the corresponding nuclear quadrupole coupling constants. The electric molecular dipole moments of the complexes have been estimated from the excitation pulse lengths, optimized for maximum signal strength (π/2 condition).