The infrared vibration-rotation spectrum of trans and cis nitrous acid

Infrared spectra of the trans and the cis isomers of nitrous acid, both HONO and DONO, have been observed in the gas phase using a Fourier transform interferometer with a resolution of about 0.05 cm−1 from 4000 to 500 cm−1. Rotational analyses are reported on eleven of the fundamentals and some overtones.

Vibration-rotation spectra and the harmonic force field of HOCl

Vibration-rotation spectra of HOCl have been measured at a resolution of 0.05 cm−1 to determine vibration rotation constants, and 35–37 Cl isotope shifts in the vibration frequencies. The spectrum of DOCl has also been recorded, and a preliminary analysis for the band origins has been made. The vibrational frequency data and centrifugal distortion constants have been used to determine the harmonic force field in a least-squares refinement; the force field obtained also gives a good fit to data on the vibrational contributions to the inertial defect. The equilibrium rotational constants of HOCl have been obtained, and an equilibrium structure has been estimated.

Vibration-rotation bands of diazomethane

Some absorption bands of diazomethane vapour between 1950-3500 cm-1 have been measured with very high resolving power. The rotational structure of two parallel bands and of one perpendicular band has been resolved, and approximate values have been determined for the rotational constants. The results are consistent with the geometrical structure usually accepted for this molecule. A peculiarity in the results for the band near 2100 cm-1, together with other facts, leads to the suggestion that a tautomeric form of this molecule exists, HCN=NH, being an isoelectronic analogue of hydrazoic acid.

Vibration-rotation spectra of nitrous acid, HONO

High-resolution Fourier-transform infrared spectra have been recorded and analyzed for the nu4, nu5, and nu6 fundamental bands of trans-HONO, and for the nu4 fundamental of cis-HONO. The spectral resolution was better than 0.01/cm, and the rotational structure has been analyzed to give improved ground-state and excited-state rotational constants, with a standard deviation of the fit to the observed line positions of around 0.0006/cm. Two Coriolis interactions have been analyzed between the nu5 and nu6 bands of trans-HONO.

Vibration-rotation spectra of 13C containing acetylene: anharmonic resonances

High resolution vibration-rotation spectra of 13C2H2 were recorded in a number of regions from 2000 to 5200 cm−1 at Doppler or pressure limited resolution. In these spectral ranges cold and hot bands involving the bending-stretching combination levels have been analyzed up to high J values. Anharmonic quartic resonances for the combination levels ν1 + mν4 + nν5, ν2 + mν4 + (n + 2) ν5 and ν3 + (m − 1) ν4 + (n + 1) ν5 have been studied, and the l-type resonances within each polyad have been explicitly taken into account in the analysis of the data. The least-squares refinement provides deperturbed values for band origins and rotational constants, obtained by fitting rotation lines only up to J ≈ 20 with root mean square errors of ≈ 0.0003 cm−1. The band origins allowed us to determine a number of the anharmonicity constants xij0.

The fundamental vibration-rotation band of hydrogen chloride

The fundamental vibration-rotational absorption band of hydrogen chloride near 3 45,t has been remeasured using higher resolving power than previously. The wave-lengths of the absorption lines have been determined more precisely, and the isotopic splitting of lines has been completely resolved. The results have provided new and more satisfactory values for the rotational constants Bi, and the centrifugal stretching constants Di, and their relative values for the two isotopic species agree closely with what is to be expected for the difference in mass. The positions of the lines in the pure rotational absorption spectrum have been calculated from the derived data, and agree closely with those recently observed. The bond lengths re for each isotopic species H35C1 and H37C1 is found to be 1-2744A.

Internal rotation in dimethylacetylene

The vibrational spectrum of dimethyl acetylene has been remeasured with better resolving power than hitherto, and the rotational fine structure of some perpendicular type bands has been partly analyzed. The energy levels of a molecule of this kind in which internal rotation of methyl groups may arise have been re-examined theoretically and the rotational structure of the absorption bands has been more clearly defined than previously. The experimental results are consistent with the assumption of unrestricted internal rotation of the methyl groups, and the Coriolis factors $\zeta _{i}$ for several vibrations have been determined.

The fundamental vibration-rotation bands of 13C16O and 12C18O

Rotation lines in the fundamental vibration bands of 13C16O and 12C180 have been measured, using very high resolving power and more accurate wavelength calibrations than previously. The molecular rotational and vibrational constants have been deduced and compared in relation to the mass differences between these molecules and the main species 12C160.

Potential surfaces from vibration-rotation data

The problems of inverting experimental information obtained from vibration-rotation spectroscopy to determine the potential energy surface of a molecule are discussed, both in relation to semi-rigid molecules like HCN, NO2, H2CO, etc., and in relation to non-rigid or floppy molecules with large amplitude vibrations like HCNO, C3O2, and small ring molecules. Although standard methods exist for making the necessary calculations in the former case, they are complex, and they require an abundance of precise data on the spectrum that is rarely available. In the case of floppy molecules there are often data available over many excited states of the large amplitude vibration, but there are difficulties in knowing the precise form of the large amplitude coordinate(s), and in allowing for the vibrational averaging effects of the other modes. In both cases difficulties arise from the curvilinear nature of the vibrational paths which are not adequately handled by our present theories.

Vibration-rotation spectra of deuterated nitrous acid, DONO

High-resolution Fourier transform infrared spectra have been recorded and analyzed for the ν3, ν4, ν5, and ν6 fundamental bands of trans-DONO, and for the ν4 fundamental of cis-DONO. The spectral resolution was better than 0.01 cm−1, and the bands have been fitted using an asymmetric top Hamiltonian with a standard deviation of around 0.0006 cm−1.

A chimeric N-terminal Escherichia coli C-terminal Rhodobacter sphaeroides FliG rotor protein supports bidirectional E coli flagellar rotation and chemotaxis

Flagellate bacteria such as Escherichia coli and Salmonella enterica serovar Typhimurium typically express 5 to 12 flagellar filaments over their cell surface that rotate in clockwise (CW) and counterclockwise directions. These bacteria modulate their swimming direction towards favorable environments by biasing the direction of flagellar rotation in response to various stimuli. In contrast, Rhodobacter sphaeroides expresses a single subpolar flagellum that rotates only CW and responds tactically by a series of biased stops and starts. Rotor protein FliG transiently links the MotAB stators to the rotor, to power rotation and also has an essential function in flagellar export. In this study, we sought to determine whether the FliG protein confers directionality on flagellar motors by testing the functional properties of R. sphaeroides FliG and a chimeric FliG protein, EcRsFliG (N-terminal and central domains of E. coli FliG fused to an R. sphaeroides FliG C terminus), in an E. coli FliG null background. The EcRsFliG chimera supported flagellar synthesis and bidirectional rotation; bacteria swam and tumbled in a manner qualitatively similar to that of the wild type and showed chemotaxis to amino acids. Thus, the FliG C terminus alone does not confer the unidirectional stop-start character of the R. sphaeroides flagellar motor, and its conformation continues to support tactic, switch-protein interactions in a bidirectional motor, despite its evolutionary history in a bacterium with a unidirectional motor.

Mental rotation in Williams syndrome: an impaired ability

Typically developing young children and individuals with intellectual disabilities often perform poorly on mental rotation tasks when the stimulus they are rotating lacks a salient component. However. performance can he improved when salience is increased. The present study investigated the effect of salience oil mental rotation performance by individuals with Williams syndrome. Individuals with Williams syndrome and matched controls were presented with two versions of a mental rotation task: a no salient component condition and a salient component condition. The results showed that component salience did not benefit individuals with Williams syndrome in the same manner as it did controls.