Franck-Hertz experiment

The current in the Franck-Hertz experiment shows a sharp change at a particular value of the accelerating voltage, corresponding to the threshold energy transfer from the electron to a gaseous atom. 

The Franck-Hertz experiment measures directly the separation between energy levels of the atom by measuring the energy lost by an electron colliding with the atom. 

The Franck-Hertz Experiment and the Energy Levels of Atoms... 

The Franck-Hertz experiment and atomic energy levels Electrons can excite atoms from one quantum state to another by energy transferred during collisions. The threshold energy for excitation exactly matches the emission of light as the atom drops back down to the lower state, thus confirming the existence of quantized states and showing that they may be excited by either mechanical impact of electrons or absorption of photons. 

In a Franck-Hertz experiment on sodium atoms, the first excitation threshold occurs at 2.103 eV. Calculate the wavelength of emitted light expected just above this threshold. (Note Sodium vapor lamps used in street lighting emit spectral lines with wavelengths 5891.8 and 5889.9 A.)... 

In a Franck-Hertz experiment on hydrogen atoms, the first two excitation thresholds occur at 10.1 and 11.9 eV. Three optical emission lines are associated with these levels. Sketch an energy-level diagram for hydrogen atoms based on this information. Identify the three transitions associated with these emission lines. Calculate the wavelength of each emitted line. 

Being the actual numerical model mainly a rationalization of the experimental facts, let s involve other estimable quantities. The IP, closely related also with the actual absolute electronegativity (4.253) definition, is a quite accessible spectral atomic index, either theoretical from the limit frequency from which the continuum spectmm is achieved, or experimentally by a Franck-Hertz experiment. Nevertheless, as far as all the valence... 

In Section 5-8 it is pointed out that the first change in plate current in the Franck-Hertz experiment with atomic hydrogen in the apparatus would occur when the voltage reached 10.2 V. To what change in principal quantum number of the electron in the hydrogen atom does this excitation correspond At what voltage would the next excitation occur (Answer , t= ton = 2 12.09 V.)... 

Franck and Hertz (1913) first demonstrated that an electron has to acquire a minimum energy before it can ionize. Thus, they provided an operational definition of the ionization potential and showed that it is an atomic or molecular property quite free from experimental artifacts. However, this kind of experiment does not tell anything about the nature of the positive ion for this, one needs a mass spectrometric analysis. Although Thompson had demonstrated the existence of H+, H2+, and H3+ in hydrogen discharge, it seems that Dempster (1916) was the first to make a systematic study of the positive ions. 

The combination of a mass analyzer with the electron impact apparatus enabled the scope of the pioneer work of Hertz, Lenard, Franck, and Lozier to be greatly extended, and results of less ambiguity were obtainable. Such experiments lead in general to a curve relating the ion current... 

We return now to the collision experiments of Franck and Hertz. We see that if the energy E of the electrons is less than tlie first excitation energy E — Eq, the atoms remain in the ground state. If E becomes greater than E — E, but remains less than Eq jBq, the atom can be brought by the collision into the first excited state, and consequently when it falls back into the ground state radiiites only... 

Bohr s fundamental concepts of discrete stationary states and a quantum frequency condition receive their most direct confirmation from a class of investigations initiated by Franck and Hertz, and subsequently extended and refined by these and other investigators. The fundamental idea of these experiments is that definite amounts of energy can be communicated to atoms by bombarding them with electrons of known velocity. As the velocity of the bombarding electrons is increased, the abrupt occurrence of the stationary states is indicated on the one hand by the sudden appearance of electrons which have lost some of their incident energy, and on the other by the sudden production of radiation of those frequencies which are associated with transitions from the stationary state in question to other stationary states of lower energy. 

Apparatus for electron-impact experiments of the sort carried out by Franck and Hertz. 

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