PubMed Health⌕ Search

Biomedical subjects

H Linnartz

Publications and source records attributed to H Linnartz.

7 recordsLinked to original sources
PubMed2006

Fermi interaction between the nu1 and the nu2+4 nu(s) bands of Ar...DN2(+).

Two rotationally fully resolved vibrational bands have been assigned unambiguously to the linear deuteron bound Ar...DN(2) (+) complex by using ground state combination differences. The ionic complex is formed in a supersonic planar plasma expansion optimized and controlled by a mass spectrometer and is detected in direct absorption using tunable diode lasers and applying production modulation spectroscopy. The band origins are located at 2436.272 cm(-1) and at 2435.932 cm(-1) and correspond to the nu(1) band (NN stretch) and to the nu(2)+4 nu(s) combination band (DN and intermolecular stretch), respectively. The two bands overlap strongly and the large intensity of the combination band is explained in terms of a Fermi interaction. This interaction perturbs the observed transitions, particularly for low J values. Least-squares fitting yields values for the Fermi interaction parameters of F(0)=0.332 cm(-1) and F(J)=-0.001 46 cm(-1) and results in accurate rotational constants. These are discussed both from an experimental and a theoretical point of view.

Journal Article↗
PubMed2005

Differential cross sections for collisions of hexapole state-selected NO with He.

The first measurements of differential inelastic collision cross sections of fully state-selected NO (j=12, Omega=12, epsilon= -1) with He are presented. Full state selection is achieved by a 2 m long hexapole, which allows for a systematic study of the effect of parity conservation and breaking on the differential cross section. The collisionally excited NO molecules are detected using a resonant (1+1') REMPI ionization scheme in combination with the velocity-mapped, ion-imaging technique. The current experimental configuration minimizes the contribution of noncolliding NO molecules in other rotational states j, Omega, epsilon--that contaminates images--and allows for study of the collision process at an unprecedented level of detail. A simple method to correct ion images for collision-induced alignment is presented as well and its performance is demonstrated. The present results show a significant difference between differential cross sections for scattering into the upper and lower component of the Lambda-doublet of NO. This result cannot be due to the energy splitting between these components.

Journal Article↗
PubMed2005

High-resolution infrared spectroscopy of the charge-transfer complex [Ar-N2]+: a combined experimental/theoretical study.

A combined experimental and theoretical study of the charge-transfer complex [Ar-N(2)](+) is presented. Nearly 50 transitions split by spin-rotation interaction have been observed by means of infrared diode laser absorption spectroscopy in a supersonic planar plasma expansion. The band origin is at 2272.2563(18) cm(-1) and rotational constants in the ground and vibrationally (NN-stretch) excited state amount to 0.128701(8) cm(-1) and 0.128203(8) cm(-1), respectively. The interpretation of the data in terms of a charge switch upon complexation is supported by new ab initio calculations. The best estimate for a linear equilibrium structure yields R(e)(NN)=1.102 A and R(e)(Ar-N)=2.190 A. Predictions for molecular parameters not directly available from the experimental results are presented as well. Furthermore, the electronic structure and Ar-N bonding mechanism of [Ar-N(2)](+) have been analyzed in detail. The Ar-N bond is a textbook example of a classical 2-center-3-electron bond.

Journal Article↗
PubMed2002

Rotationally resolved infrared spectrum of the charge transfer complex [Ar-N2]+.

Difficulties in preparing cluster ions for spectroscopic studies have limited our understanding of intermolecular forces in charged complexes that are typical of many reactive intermediates. Here, the infrared spectrum of the charge transfer complex [Ar-N2]+, recorded in a supersonic planar plasma with a tunable diode laser spectrometer, is presented. More than 70 adjacent rovibrational transitions were measured near 2272 wave numbers and assigned to the molecular nitrogen stretching fundamental in the 2Sigma+ ground state of [Ar-N2]+. The accurate structural parameters that were determined confirm a linear structure and show that the major part of the charge is located at the argon atom. The latter result is surprising and implies a charge switch of the cationic center upon complexation.

Journal Article↗
PubMed1999

Electronic Ground and Excited State Spectroscopy of C(6)H and C(6)D.

Rotational transitions in the X(2)Pi ground state of C(6)H and C(6)D have been measured by Fourier transform microwave and millimeter-wave absorption spectroscopy. More than 150 rotational lines in the ground (2)Pi(3/2) and (2)Pi(1/2) ladders have been observed, allowing an accurate determination of the rotational, fine structure, lambda-doubling, and hyperfine coupling constants using a standard effective Hamiltonian for a molecule in an isolated (2)Pi electronic state. The molecular ground state constants are used to characterize the rotationally resolved origin band of the (2)Pi <-- X(2)Pi electronic transition observed by cavity ring-down laser absorption spectroscopy in a pulsed supersonic slit-jet discharge source. From these data, spectroscopic constants for the excited electronic state are determined. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Tunable Far-Infrared Spectroscopy of 82KrD+, 84KrD+, 86KrD+, and 82KrH+

Pure rotational spectra of isotopic species of protonated krypton 82KrD+, 84KrD+, 86KrD+, and 82KrH+ were observed in the 0.75-3.5 THz region, using a tunable far-infrared radiation source. Rotational parameters B, D, and H of these molecular ions were determined. By analyzing the observed frequencies with the previous data on all the isotopic species, the mass independent Dunham parameters Ukl, DeltaKrkl, and DeltaHkl have been improved. Copyright 1998 Academic Press.

Journal Article↗