Kinetic energy partition method applied to ground state helium-like atoms

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been used to investigate the decay dynamics of the valence electronic states of the parent cation of several hydrofluorocarbons (HFC), based on fluorine-substituted ethane, in the energy range 11–25 eV. We present data for CF 3– CHF 2, CF 3– CH 2 F , CF 3– CH 3 and CHF 2– CH 3. The threshold photoelectron spectra (TPES) of these molecules show a common feature of a broad, relatively weak ground state, associated with electron removal from the highest-occupied molecular orbital (HOMO) having mainly C–C σ-bonding character. Adiabatic and vertical ionisation energies for the HOMO of the four HFCs are presented, together with corresponding values from ab initio calculations. For those lower-energy molecular orbitals associated with non-bonding fluorine 2pπ lone pair electrons, these electronic states of the HFC cation decay impulsively by C–F bond fission with considerable release of translational kinetic energy. Appearance energies are presented for formation of the daughter cation formed by such a process (e.g. CF 3– CHF +), together with ab initio energies of the corresponding dissociation channel (e.g. CF 3– CHF + + F ). Values for the translational kinetic energy released are compared with the predictions of a pure-impulsive model.

Download Full-text

Figuring Out Gas & Galaxies In Enzo (FOGGIE). V. The Virial Temperature Does Not Describe Gas in a Virialized Galaxy Halo

The Astrophysical Journal ◽

10.3847/1538-4357/ac2496 ◽

2021 ◽

Vol 922 (2) ◽

pp. 121

Author(s):

Cassandra Lochhaas ◽

Jason Tumlinson ◽

Brian W. O’Shea ◽

Molly S. Peeples ◽

Britton D. Smith ◽

...

Keyword(s):

Kinetic Energy ◽

Surface Brightness ◽

Radiative Cooling ◽

Low Density ◽

Energy Partition ◽

X Ray ◽

Stellar Feedback ◽

Galaxy Halo ◽

Definition Of ◽

Halo Gas

Abstract The classical definition of the virial temperature of a galaxy halo excludes a fundamental contribution to the energy partition of the halo: the kinetic energy of nonthermal gas motions. Using simulations of low-redshift, ∼L* galaxies from the Figuring Out Gas & Galaxies In Enzo (FOGGIE) project that are optimized to resolve low-density gas, we show that the kinetic energy of nonthermal motions is roughly equal to the energy of thermal motions. The simulated FOGGIE halos have ∼2× lower bulk temperatures than expected from a classical virial equilibrium, owing to significant nonthermal kinetic energy that is formally excluded from the definition of T vir. We explicitly derive a modified virial temperature including nonthermal gas motions that provides a more accurate description of gas temperatures for simulated halos in virial equilibrium. Strong bursts of stellar feedback drive the simulated FOGGIE halos out of virial equilibrium, but the halo gas cannot be accurately described by the standard virial temperature even when in virial equilibrium. Compared to the standard virial temperature, the cooler modified virial temperature implies other effects on halo gas: (i) the thermal gas pressure is lower, (ii) radiative cooling is more efficient, (iii) O vi absorbing gas that traces the virial temperature may be prevalent in halos of a higher mass than expected, (iv) gas mass estimates from X-ray surface brightness profiles may be incorrect, and (v) turbulent motions make an important contribution to the energy balance of a galaxy halo.

Download Full-text

Stimulated Processes in a Half-collision

Laser Chemistry ◽

10.1155/lc.5.393 ◽

1986 ◽

Vol 5 (6) ◽

pp. 393-406

Author(s):

H. H. Telle

Keyword(s):

Kinetic Energy ◽

Quantum State ◽

Ground State ◽

Diatomic Molecules ◽

Dye Laser ◽

Interatomic Potentials ◽

Repulsive Potential ◽

Induced Absorption ◽

Tunable Dye Laser

Selective photodissociation of diatomic molecules is used to prepare the separating species in a well defined quantum state with narrowly determined final kinetic energy of the particles. During the course of separation to products the repulsive potential is probed by a tunable dye laser, that is by induced absorption in case the dissociation proceeds on a potential leading to ground state products, or by induced emission or absorption for all other cases. The determination of interatomic potentials from the observed spectra is discussed.

Download Full-text

Dissociative Electron Attachment Processes in SO2 and NO2

Canadian Journal of Chemistry ◽

10.1139/v71-255 ◽

1971 ◽

Vol 49 (9) ◽

pp. 1571-1574 ◽

Cited By ~ 12

Author(s):

D. A. Rallis ◽

J. M. Goodings

Keyword(s):

Kinetic Energy ◽

Ground State ◽

Electronic Excitation ◽

Electron Attachment ◽

Negative Ion ◽

Dissociation Limit ◽

Dissociative Electron Attachment ◽

Zero Kinetic Energy ◽

Trapped Electron ◽

Second Peak

A trapped electron apparatus has been used to identify the processes involved in negative ion formation for the triatomic oxides SO2 and NO2. Two O− peaks are observed in SO2 with onset values at 4.2 ± 0.15 and 6.3 ± 0.2 eV, and peak values at 5.0 ± 0.15 and 7.4 ± 0.15 eV, respectively. From kinetic energy analysis of the O− ions, both peaks are found to have the same dissociation limit involving SO in its ground state. For NO2, two dissociative electron attachment peaks are observed with onset values at 1.6 ± 0.2 and 7.3 ± 0.3 eV, and peak values at 3.0 ± 0.2 and 8.1 ± 0.2 eV, respectively. The first broad peak is explained by overlapping contributions from two processes having the same dissociation limit involving ground state NO; they differ only in the amount of kinetic energy possessed by the fragments. The second peak appears to involve electronic excitation of the neutral fragment NO* with zero kinetic energy at onset.

Download Full-text