Spontaneous decay transition

We use a7r/2 — vr — vr/2 pulse sequence to coherently divide, deflect and finally recombine an atomic wavepacket. The first vr/2 pulse excites an atom initially in the l,p) state into a coherent superposition of states l,p) and 2,p + hkeff). If state 2) is stable against spontaneous decay, the two parts of the wavepacket will drift apart by a distance hkT/m in time T. Each partial wavepacket is redirected by a vr pulse which induces the transitions... 

The rate of spontaneous decay increases with v3 so that for higher frequency transitions, such as in the visible region of the spectrum, spontaneous decay is fast (of the order of nanoseconds) whereas rotational transitions or transitions between hyperfine levels within an atom are very slow. 

Fig. 16.8 Schematic illustration of the magnetic resonance technique used to measure the Rb nf fine structure intervals. The Rb atoms in the n2F states are populated by spontaneous decay of the n D5/2 states, which are populated by stepwise excitation of the ground state atoms. The rf transitions, induced among the magnetic sublevels of the n2F states, are detected as a change in the intensity of the polarized n2F — 42D fluorescence. The lower part of the figure shows a sketch of the experimental arrangement (from ref. 36).

Laser induced transition probabilities are often small. This is because the interaction time of the ions with the laser is short ( ns), and because the relevant matrix elements are small, or else the levels involved have large natural widths. A useful approximate expression for estimating signal strengths for an electric-dipole (El) transition from a metastable level 1) to a short lived level 2), followed by a spontaneous decay to a third level 13), when the interaction time is long compared to the lifetime of the second level is [8] ... 

The rate of radiative spontaneous decay. To, of a dipole transition of frequency ro and dipole momentum J in a point-like emitter, such an atom or a molecule, embedded into a dielectric host of permittivity Shost, is described by well-known expression (speed of light... 

The interest in quantum interference stems from the early 1970s when Agarwal [4] showed that the ordinary spontaneous decay of an excited degenerate V-type three-level atom can be modified due to interference between the two atomic transitions. The analysis of quantum interference has since been extended to other configurations of three- and multilevel atoms and many interesting effects have been predicted, which can be used to control optical properties of quantum systems, such as high-contrast resonances [5,6], electro-magnetically induced transparency [7], amplification without population inversion [8], and enhancement of the index of refraction without absorption [9]. 

Consider the weak-field limit where Q is much smaller than the spontaneous decay rates and assume, for simplicity, that the decay rates of the upper levels on the visible and ultraviolet transitions are equal, Tv = Tu = T. In this case, we can solve the system analytically, and find that the steady-state populations and coherences appearing in Eq. (164) are... 

S2- 515 lasing was-obtained within 0.5 ys. As a result, sufficient population buildup occurred in 5 to achieve 515- 516 oscillation before significant spontaneous decay from the 5l5 state. Cascade lasing schemes of Ho3+ in Gd3Ga50]2 crystals including 16 18 transitions were reported recently (Z8). 

Figure 6. A simplified diagram showing the 4 basic parts of an FTMW spectrometer. The signal generator transmits a pulse of microwave radiation into the Fabry-Perot cavity. The molecules absorb the radiation through excitation of a rotational transition, and then spontaneously decay. The echo signal from the molecules is amplified and then detected as a function of time,...

If a two-level atom is positioned at x in free space with the transition dipole parallel to the z-axis, in the dipole approximation the resulting spontaneous decay rate is given by... 

The becquerel (Bq), the SI unit of activity, is the activity of a radionuclide decaying at a rate, on average, of one spontaneous nuclear transition per second. Thus 1 Bq = 1 s . The former unit, the curie (Ci), is equal to 3.7 x 10 Bq. The curie was originally chosen to approximate the activity of 1 gram of radium-226. 

Observation of cavity-induced enhancement and inhibition of spontaneous decay have been reported by a number of groups for microwave transitions between Rydberg levels of alkali atoms. In a... 

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