Doublets population

Bruno, A.E., Briihlmann, U., and Huber, J.R. (1988). Photofragmentation LIF spectroscopy of NOCL at dissociation wavelengths > 450 nm. Parent electronic spectrum and spin state and A-doublet populations of nascent NO and CL fragments, Chem. Phys. 120, 155-167. 

Quinton, A.M. and Simons, J.P. (1981). A-doublet population inversions in NH(c1n) excited through vacuum ultraviolet dissociation of NH3, Chem. Phys. Lett. 81, 214-217. 

Schwartz-Lavi, D., Bar, I., and Rosenwaks, S. (1986). Rotational alignment and non-statistical A doublet population in NO following (CHs CONO photodissociation, Chem. Phys. Lett. 128, 123-126. 

Pli Q21 branches. The A doublets population will be discussed later. 

Significant differences have been found in the vibration- rotation distribution of excited N2(C Ilu) molecules formed by excitation transfer from Ai<3pq 2 ) to nitrogen molecules [109,110]. A somewhat hotter vibrational distribution is found for the 3 PqO incident level from variable temperature studies, this is ascribed, at least in part, to energy resonance effects [110]. Unequal N2(C) spin and A doublet populations, which also depended on the Ar initial level, were deduced from high-resolution studies of die C-B emission [109]. These variations gave rise to an even-odd N alternation in the rotational populations and were explained as arising from dynamical constraints, including the dominance of planar ArNN collisions and the preferential population of A doublets whose electronic distribution is symmetric with respect to reflection in the plane of rotation. 

A-doublet components, the electron density tends to lie in (peipendicular to) the plane of rotation, i.e. perpendicular (parallel) to J. Unequal A-doublet populations therefore reflect preferential electronic oibital alignments, for example in NO or OH(x2ri3/2,i/2) N2 (C IIo,2) alignment of J with respect to the exit... 

The A-doublet population inversion in the J = 1/2 and 3/2 levels of NH (X Ilr) and excitation of MW emission by collisions with H atoms (expected to occur in interstellar clouds) was treated by a scattering theoretical approach [7, 8]. 

These are the same states as in Figure Bl.l 1.8, but attention is now drawn to the populations of the four spin states, each reduced by subtracting the 25% population that would exist at very low field, or alternatively at infinite temperature. The figures above each level are these relative differences, in convenient units. The intensity of any one transition, i.e. of the relevant peak in the doublet, is proportional to the difference of these differences, and is therefore proportionally relative to unity for any transition at Boltzmaim equilibrium, and 4 for any transition. 

A major discrepancy that remains unresolved in the excited-state properties of the [Fe384]° cluster in D. gigas Fdll concerns the existence of a low-lying, fully valence-delocalized state that becomes populated at temperatures above 25 K. 8uch a state is clearly apparent in the temperature-dependent Mossbauer studies of reduced D. gigas Fdll (29) and P. furiosus 3Fe Fd (198) and is represented by one quad-rupole doublet with AEq 0.9 mm/s and S = 0.45 mm/s. 8uch a... 

Figure 2.9 Pulse sequence for the INEPT experiment. (B) Effect of pulses on H magnetization. Application of the pulse sequence shown results in population inversion of one of the two proton vectors of the CH doublet and therefore causes an intensification of the corresponding C lines.

FIGURE 4.1 Boltzmann population of a doublet as a function of temperature. The lower and the higher level of the doublet have population n0 and n1 respectively, and they are separated by an energy difference of 0.3 cnr1. 

The lithium resonance doublet line X 6707 is fairly easy to observe in cool stars of spectral types F and later, and it has also been detected in diffuse interstellar clouds. There is thus an abundance of data, although in the ISM the estimation of an abundance is complicated by ionization and depletion on to dust grains. The youngest stars (e.g. T Tauri stars that are still in the gravitational contraction phase before reaching the main sequence) have a Li/H ratio that is about the same as the Solar System ratio derived from meteorites, Li/H = 2 x 10-9, which is thus taken as the Population I standard. 

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