Determining nuclear hyperfine populations in the ground electronic state of atomic hydrogen produced by the 193 nm photolysis of HBr

1995 ◽  
Vol 103 (13) ◽  
pp. 5864-5867 ◽  
Author(s):  
Kenneth A. Cowen ◽  
K. Thomas Lorenz ◽  
Yu‐Fong Yen ◽  
Michael F. Herman ◽  
Brent Koplitz
Keyword(s):  
Electronic State ◽  
Atomic Hydrogen ◽  
Ground Electronic State ◽  
193 Nm

Infra-red chemiluminescence I. Infra-red emission from hydrogen chloride formed in the systems atomic hydrogen plus chlorine, atomic hydrogen plus hydrogen chloride, atomic hydrogen plus deuterium chloride, and atomic deuterium plus hydrogen chloride

1960 ◽  
Vol 258 (1295) ◽  
pp. 529-563 ◽  
Keyword(s):  
Electronic State ◽  
Hydrogen Chloride ◽  
Atomic Hydrogen ◽  
Room Temperature ◽  
Ground Electronic State ◽  
Third Body ◽  
Vibrationally Excited ◽  
Red Emission ◽  
Vibrational Levels ◽  
Infra Red

Infra-red emission arising from several room-temperature gas-phase reactions has previously been described by the authors in preliminary communications (Cashion & Polanyi 1958, 1959 a, b, c ). In the present work, details of this new technique are given. Spectra obtained from the systems H + Cl 2 , H + HCl, H + DCl and D + HCl are described. These consist of the resolved spectra of the HCl fundamental transitions (∆ v = 1) in the ground electronic state, the partially resolved first overtones (∆ v = 2) and, in one system, the unresolved second overtones (∆ v = 3). The system H + Cl 2 gives rise to emission from all vibrational levels up to and including v = 6; the system H + HCl from all levels up to and including v = 7. A detailed examination of the spectra obtained from the systems H + HCl, H + DCl and D + HCl leads to the conclusion that these emissions arise from the formation of vibrationally excited HCl or DCl as the product of an association reaction between hydrogen atoms and chlorine atoms (in the presence of some ‘third body’, M ). This result constitutes the first direct evidence for the view that association reactions lead to the formation of highly vibrating molecules (Polanyi 1959). Also consistent with this view is the observation made here that HCl or DCl acting as a third body in association reactions is not excited to levels higher than v = 1. The bulk of the emission observed from the system H + Cl 2 is believed to arise from the exchange reaction H + Cl 2 = HClꜛ v ≼ 6 + Cl (where HClꜛ is vibrationally excited HCl in its ground electronic state). The vibrational distribution of HClꜛ in the system H + Cl 2 , under our experimental conditions, conforms approximately to a Boltzmann distribution for a vibrational temperature of 2700°K. From this observed distribution a calculation of the initial distribution is made, which would indicate that the HClꜛ are formed initially in all accessible vibrational levels, lower levels being favoured over higher. However, this result is based on the arbitrary assumption that vibrational-vibrational exchange between HClꜛ molecules is negligible. The distribution of HClꜛ among rotational levels of v = 1 in the system H + Cl 2 is definitely non-Boltzmann. The excess rotational energy over room temperature equilibrium energy, is shown to come from an even greater excess present in the HClꜛ as originally formed. The absolute intensity of the emission is calculated at ca . 0.005 W. It is estimated that roughly 1 to 10 % of the heat of reaction goes into vibrational excitation.

The gauche Effect. A Theoretical Study of the Topomerization (Degenerate Racemization) and Tautomerization of Methoxide Ion Tautomer

1973 ◽  
Vol 51 (15) ◽  
pp. 2423-2432 ◽  
Author(s):  
Saul Wolfe ◽  
Luis M. Tel ◽  
I. G. Csizmadia
Keyword(s):  
Electronic State ◽  
Ground Electronic State ◽  
Conformational Transformation ◽  
Molecular Orbital Calculations ◽  
Rotational Angle ◽  
Electron Pairs ◽  
Hydroxyl Proton ◽  
Gauche Effect ◽  
Internuclear Distances ◽  
Relationship Of

Non-empirical double zeta quality molecular orbital calculations on −CH2OH as a function of the C—O bond length (r), the rotational angle about the C—O bond (θ), and the pyramidal angle at carbon [Formula: see text] are described. From the stretching potential curve, E(r), it is shown that dissociation of −CH2OH proceeds to give CH2 and OH−. The rotation–inversion surface, [Formula: see text], has two types of minima; in both cases the most favorable pyramidal angle at carbon is 105°. The lower minimum corresponds to a structure (the Y conformation) having the hydroxyl proton on the external bisector of the HCH angle. The higher minimum is 6.67 kcal/mol less stable and corresponds to a structure (the W conformation) having the hydroxyl proton on the internal bisector of the HCH angle. The relationship of these results to the gauche effect is discussed and it is noted that at certain internuclear distances the nuclear–nuclear repulsion term (Enucl) may overcome the tendency of adjacent electron pairs and polar bonds to exist preferentially in that conformation which has the maximum number of gauche interactions between these electron pairs or polar bonds.The topomerization of −CH2OH, i.e., the conformational transformation from one Y conformation into another, proceeds, via the W conformation as an intermediate, by two separate events, viz. rotation about the C—O bond, having a barrier of 10.58 kcal/mol, and pyramidal inversion at carbon, with a barrier of 20.52 kcal/mol. Some factors governing the relative importance of rotation and inversion in degenerate racemization are discussed.In its ground electronic state CH3O− is 22.18 kcal/mol more stable than −CH2OH. However, in the low-lying excited states all conformations of −CH2OH are stabilized relative to CH3O−. The most stable excited state structure of −CH2OH corresponds to the energy maximum for rotation–inversion of the ground electronic state.

Quantum dynamics of the photostability of pyrazine

2015 ◽  
Vol 17 (44) ◽  
pp. 29518-29530 ◽  
Author(s):  
Matthieu Sala ◽  
Stéphane Guérin ◽  
Fabien Gatti
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Quantum Dynamics ◽  
Ground Electronic State ◽  
Conical Intersection ◽  
Radiationless Decay

We propose a new mechanism for the radiationless decay of photoexcited pyrazine to its ground electronic state involving a conical intersection between the dark Au(nπ) state and the ground state.

Microwave spectrum of HSiO in the X2A′ ground electronic state

1997 ◽  
Vol 413-414 ◽  
pp. 527-535 ◽  
Author(s):  
Mitsuaki Izuha ◽  
Satoshi Yamamoto ◽  
Shuji Saito
Keyword(s):  
Electronic State ◽  
Microwave Spectrum ◽  
Ground Electronic State

Direct photoionization measurements of slow decay rates of vibrationally overexcited (CF3)3CI molecules in the ground electronic state in a beam

1986 ◽  
Vol 127 (5) ◽  
pp. 438-444 ◽  
Author(s):  
V.M. Apatin ◽  
V.S. Letokhov ◽  
V.N. Lokhman ◽  
G.N. Makarov ◽  
V.N. Bagratashvili ◽  
...  
Keyword(s):  
Electronic State ◽  
Decay Rates ◽  
Ground Electronic State ◽  
Slow Decay
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