Energy distributions of /sup 181/Ta ..gamma.. rays absorbed by a resonance absorber have been measured for two values of the duration of the wave packets larger and smaller than the lifetime of the isomeric level of the nucleus. The wave packets were produced by mechanical chopping of the radiation. The results of the measurements are in good agreement with a calculation carried out on the assumption ..delta omega..x..delta..tapprox.1.
Energy distributions of /sup 181/Ta ..gamma.. rays absorbed by a resonance absorber have been measured for two values of the duration of the wave packets larger and smaller than the lifetime of the isomeric level of the nucleus. The wave packets were produced by mechanical chopping of the radiation. The results of the measurements are in good agreement with a calculation carried out on the assumption ..delta omega..x..delta..tapprox.1.
The well-known narrowing of the Mössbaur γ-line with increasing age of the excited energy state ℏω0 of the emitter nucleus (the half-life is T1/2) and broadening of the γ-line with decreasing irradiation time of the absorber nucleus are analyzed. Taking into account the short time of emission of quantum transition energy – much less than T1/2, which can be seen, for example, from the duration of the γ-signal on the scintillator, the analysis leads to the idea of the structure of the γ-quantum (photon) as an electromagnetic wave of frequency ω0 that does not carry energy (0-wave), which is emitted by the nucleus from the moment of formation of the excited state to the quantum transition, with the energy quantum ℏω0 in the form of a short-term singularity on the “tail” of this 0-wave. A possible source of 0-waves can be virtual transitions of the nucleus from the excited state to the ground state and back before the emission of an energy quantum. Detection of 0-waves is possible due to changing the width of the γ‑line with additional irradiation of the absorber nuclei by resonant 0-waves. The possibility of predicting the future decay of an excited state by 0-waves detecting and the prospects of using 0-waves for information transmission are noted. The principle of a 0-wave generator without energy radiation is proposed.
We report the generation of sidebands in the energy spectrum of 14.4-keV $\ensuremath{\gamma}$ rays by a periodic modulation of the properties of the medium between the emitting and absorbing atoms. The observed spectrum agrees in detail with a "chopping" calculation that encompasses both amplitude and phase modulation, although the modulator may equally well be viewed as a moving multislit grating. This is the first experiment in which the observed sidebands in the $\ensuremath{\gamma}$-ray spectrum have been quantitatively understood.
In the present paper, we see the manner of the propagation of the wave packet in the presence of a scatterer and we see the form of the scattered packet. The form of the scattered packet at the detector is closely related to the form of the energy spectra. The general form of the energy spectra is given in connection with the wave packet nature of the scattered beam. Of course, this energy spectra tends to the conventional Lorentzian type in the stationary limit. In Part I of the present paper, the relation between the form of the scattered packet and the cross section is discussed in detail. In Part II, we see the relation between the average procedure of the cross section and the optical model, in terms of the wave packet. In general, the scattered packet draggles the tail of life 1/Γ, Γ being the level width, as well as fluctuations appearing in the transient state. If we average the cross section over many sharp resonances, these fluctuations and the tail in the scattered packet are washed out. Then, it seems as if a part of the initial beam were absorbed by this washing procedure. The remaining part is the shape elastic scattering and the dust which is washed out constitutes the compound elastic scattering. If the compound system is excited to organize the single particle mode as well as the compound nucleus mode, the fluctuation and the tail characteristic of the single particle mode is not washed out by the average procedure, provided that the energy range of the procedure is much smaller than the single particle level distance. Then in the shape elastic scattering obtained after the average procedure, only the feature of the single particle mode with the partial seeming absorption remains. This accounts for the optical model.
We propose a technique of ultra-short $\ensuremath{\gamma}$-ray pulses production with a pulse duration much less than the natural lifetime of a nucleus excited state. The technique is based on compression of frequency modulated radiation of a Mossbauer source while propagating in a far-detuned resonant absorber. Numerical estimates for 57Fe 14.413 keV nuclear resonance energy show feasibility of experimental realization of the technique
The radiation burst from a single $\ensuremath{\gamma}$-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al. [Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ``gamma echo.'' The echo is generated by a 180${}^{\ensuremath{\circ}}$ phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.
It has already been noted (section 2.8) that high frequency electromagnetic radiation can exhibit particle-like behaviour. For example, in the sensitive type of detector known as a photomultiplier tube (described in Wehr and Richards, Physics of the Atom , 2nd edn, Addison-Wesley, section 10.5), a beam of low-intensity X-rays is detected as a sequence of isolated sharp pulses, such as would be produced by a stream of particles arriving at the detector. As was pointed out, it is not surprising that it is usually high-frequency radiation which travels in particle form; as shown in figure 2.39, a wave group of high-frequency radiation can be compressed into a very short time span. However, when we speak of a particle, we mean something more than an entity which arrives in a short time span. A particle has a definite size, or more exactly it has a well-defined energy and momentum. It was discovered around about 1900 that the same is true of an X-ray wave packet: all packets of a given frequency radiation carry the same energy and momentum. This revolutionary discovery means that we must treat the wave packets as particles on exactly the same footing as more familiar particles such as electrons. The electromagnetic particle is called a photon . There is a wealth of experimental evidence which may be used to define the properties of a photon. We shall be highly selective, however, and simply present two particularly clear-cut experiments, the photoelectric effect and Compton scattering, which enable one to define the energy and momentum of the photon in terms of the frequency and wave number of the corresponding wave. These experiments will be described in detail in section 4.1.