Isotopic Analysis of Lead at Ultratrace Levels Using Thermal Ionization Mass Spectrometry (TIMS) Coupled with the Continuous Heating Method: Optimization of the Data Integration Range and Method.

This study systematically and experimentally evaluates data integration methods for the isotopic analysis of Pb at ultratrace levels using thermal ionization mass spectrometry (TIMS) with a continuous heating method. The evaluation utilized a certified reference material of Pb (SRM 981). The experimental evaluations encompass different data calculation methods (methods I, II, and III) and integration ranges (full, over 1%, 25%, and 75%).

Experimental Observation of the Autler-Townes Splitting in Polyatomic Molecules.

Autler-Townes (AT) splitting has been experimentally observed in the optical transition between the zero-point levels of S and S for supersonically cooled 2-methoxythiophenol, 2-fluorothiophenol, and 2-chlorothiophenol. This is the first experimental observation of the light-dressed quantum states of polyatomic molecules ( > 3) in the electronic transition. In the resonance-enhanced ionization process involving the optically coupled states, if Rabi cycling is ensured within the nanosecond laser pulse, AT splitting is clearly observed for the open system for which the excited-state lifetime is shorter than hundreds of picoseconds.

Conformer Specific Excited-State Structure of 3-Methylthioanisole.

and conformers of 3-methylthioanisole have been spectroscopically investigated to reveal the conformer specific structural changes upon the S(ππ*)-S excitation. The conformational cooling during the supersonic expansion is found to be quite efficient in the Ar carrier gas giving the conformational isomer exclusively in the molecular beam, whereas both and conformers are populated in the jet when the sample is carried in Ne. Using the Stark deflector, and conformers are unambiguously identified, showing the distinct Stark deflection profiles according to their sufficiently different dipole moments of 1.

Vibronic structure and predissociation dynamics of 2-methoxythiophenol (S): The effect of intramolecular hydrogen bonding on nonadiabatic dynamics.

Vibronic spectroscopy and the S-H bond predissociation dynamics of 2-methoxythiophenol (2-MTP) in the S (ππ) state have been investigated for the first time. Resonant two-photon ionization and slow-electron velocity map imaging (SEVI) spectroscopies have revealed that the S-S transition of 2-MTP is accompanied with the planar to the pseudoplanar structural change along the out-of-plane ring distortion and the tilt of the methoxy moiety. The S vibronic bands up to their internal energy of ∼1000 cm are assigned from the SEVI spectra taken via various S vibronic intermediate states with the aid of ab initio calculations.

Experimental observation of nonadiabatic bifurcation dynamics at resonances in the continuum.

The surface crossing of bound and unbound electronic states in multidimensional space often gives rise to resonances in the continuum. This situation happens in the πσ*-mediated photodissociation reaction of 2-fluorothioanisole; optically-bright bound S (ππ*) vibrational states of 2-fluorothioanisole are strongly coupled to the optically-dark S (πσ*) state, which is repulsive along the S-CH elongation coordinate. It is revealed here that the reactive flux prepared at such resonances in the continuum bifurcates into two distinct reaction pathways with totally different dynamics in terms of energy disposal and nonadiabatic transition probability.

Photodissociation Dynamics of Ortho-Substituted Thiophenols at 243 nm.

The photoinduced S-H (D) bond fission dynamics of four ortho-substituted thiophenols, 2-fluoro, 2-chloro, 2-bromo, and 2-methoxythiophenol at a pump wavelength of 243 nm, have been investigated by velocity-map imaging and high-level electronic structure calculations. The D atom images of the deuterated ortho-substituted thiophenols show much reduced X̃/Ã branching ratios of the cofragment radicals over that of bare thiophenol. The angular distributions of the D fragment display negative anisotropies, indicating that transition dipole moments are perpendicular to the fast dissociating S-D bond axis.

Spatial Isolation of Conformational Isomers of Hydroquinone and Its Water Cluster Using the Stark Deflector.

Conformational isomers of hydroquinone and their 1:1 clusters with water have been spatially separated using a Stark deflector in a supersonic jet. trans-Hydroquinone (HyQ) conformer with zero dipole moment is little influenced by inhomogeneous electric fields, whereas cis conformer with nonzero dipole moment (2.38 D) is significantly deflected from the molecular beam axis into the direction along which the strong field gradient is applied.

Alternative method of oral dosing for rats.

Oral administration of drugs to laboratory rodents typically is achieved by using the gavage technique. Although highly effective, this method occasionally can cause esophageal injury as well as restraint-associated distress, particularly with repeated use. The aim of this study was to assess an alternative oral dosing method that could reduce the distress and morbidity associated with standard gavage techniques.