Aims. The aim of this work is to verify whether turbulent magnetic reconnection can provide the additional energy input required to explain the up to now only poorly understood ionization mechanism of the diffuse ionized gas (DIG) in galaxies and its observed emission line spectra. Methods. We use a detailed non-LTE radiative transfer code that does not make use of the usual restrictive gaseous nebula approximations to compute synthetic spectra for gas at low densities. Excitation of the gas is via an additional heating term in the energy balance as well as by photoionization. Numerical values for this heating term are derived from three-dimensional resistive magnetohydrodynamic two-fluid plasma-neutral-gas simulations to compute energy dissipation rates for the DIG under typical conditions. Results. Our simulations show that magnetic reconnection can liberate enough energy to by itself fully or partially ionize the gas. However, synthetic spectra from purely thermally excited gas are incompatible with the observed spectra; a photoionization source must additionally be present to establish the correct (observed) ionization balance in the gas.
The thermodynamic properties of hydrogen bonding among lactams with ring sizes n \ 4, 5 and 6 were investigated using infrared spectroscopy of the fundamental NÈH stretching frequencies of both the monomer and dimer species. The results are consistent with a predominantly monomerÈdimer equilibrium with the dimer having symmetry. The thermodynamic properties (in for the four-, Ðve-and six-membered C 2 CCl 4 ) lactam rings are (at 25 ¡C) \ 12.4(9), 24(6) and 25(3), (kJ mol~1) \ [30(2), [30(1) and [28(2) and K d *H d (J mol~1 K~1) \ [79(4), [74( 3) and [67(5), respectively (precisions in parentheses). The experimentally *S d determined thermodynamic properties are compared with ab initio calculations (6È31G** basis set) which represent gas-phase results. The comparison of these two approaches yields a picture which is consistent with the notion that the primary e †ect of ring size is an entropy of solvation e †ect and not the enthalpy of hydrogen bonding between the monomer units.
A preliminary rotation-vibration analysis of the n = 0 and n = I subbands associated with the nV6 + VI-nV6 hydrogen-bonded vibration in HCN• .. HF has been completed. The following excited state rotational constants B' and band origin frequencies V 0 have been determined for the complex. States n=O n=l 3716.20(2) 3720.21(1) 0.12206(5) 0.12326(1) The results are consistent with a rotation-vibration interaction constant a I =-68.3 ± I MHz which correlates with an excited state r(N••.F) internuclear distance of 2.762 A, a decrease of 0.034 A relative to the ground state. Excited state lifetimes associated with assigned transitions are demonstrated to be ;::>: 1.8 X 1O-lO s while the x 16 anharmonic constant is evaluated to be 4.01 ±0.03 em-I.
A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bond dissociation energies Do and De. Results for HCN--HF give aDo = 20.77 (22) and De = 28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and ab initio molecular orbital calculations. Rovibrational band information available for HCN--HF also permits evaluation ofthermal functions of dimer formation in kJ/mol: aU;98.2 = 20.1(2), l:Jl;98.2 = 22.6(2), aG;98.2 = 59.4(2), M;98.2 = -0.1235.
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