Trivalent neodymium

Boulon G (2004) Optical Transitions of Trivalent Neodymium and Chromium Centres in LiNb03 Crystal Host Material 107 1-25... 

Trivalent neodymium has f3 configuration and has 41 energy levels. Because of the large number of levels, the absorption spectra of Nd(III) in crystals and solutions contain many bands due to the transitions from ground state 4Ig/2 to the excited levels [142], The assignment of transitions of Nd3+ in the absorption spectrum of Nd3q ion is given in Fig. 8.18. 

The neodymium laser is popular because it is a solid state laser. Trivalent neodymium ions are incorporated in a host crystal or glass, at about one atomic percent doping. In the solid state, high concentrations of ions are available as opposed to the gaseous state. Further the host crystal provides mechanical strength and chemical inertness. 

The trivalent neodymium ion is a good example of a four-level laser system. The trivalent Nd3+ system is illustrated in Fig. 12.12 in a schematic fashion. 

Trivalent neodymium absorbs strongly in broad bands in the green, red and near infra-red with reasonable coincidence in the output of a xenon flash lamp. Nearly all the electrons excited into the pump bands revert to the metastable upper level 4F3/2 through non-radiative decay which has a lifetime of 230 ps. Radiative transition then occurs to a set of lower energy levels 4I)5/2,4Ii3/2,4I 1/2,4l9/2- All these levels are multiplets and the lowest of 4l9/2 is... 

Fig. 6. The emission spectra of trivalent neodymium and ytterbium (alone, or mixed) in germanate and tellurite glasses at room temperature. It is noted that the two emission bands of neodymium almost disappear, when energy is transferred to the luminescent ytterbium. The Figure is reproduced with permission of Chemical Physics Letters211...

Two photo-excited states of trivalent neodymium in LaCl3 have been investigated... 

The structure of the trivalent neodymium fluoride species in the melt is the octahedral [NdFfi] complex anion identified by Raman spectroscopy [13]. The dissolution of Nd203 results in the formation of neodymium oxyfluorides in the melts. It also has been found that the [NdOFs]" is present [10]. Actually, [NdFe] and [NdOFs]" " coexist in the melt since the concentration of NdF3 is much... 

The first lasers-ruby and helium-neon - appeared in 1960. In the following year the use of rare earths for lasers began with divalent samarium in Cap2 (Sorokin and Stevenson, 1961), and trivalent neodymium in CaW04 (Johnson and Nassau, 1961) and in glass (Snitzer, 1961). The first liquid material to exhibit laser action was a rare earth chelate (Lempicki and Samelson, 1963). Investigations of rare earth laser action in various hosts proliferated in the 1%0 s. Additional laser transitions and material developments have continued to emerge in the 1970 s. This research has resulted in the diversity of rare earth lasers cited above. 

To illustrate the spectroscopic features of rare earth ions, in the following and throughout this section we shall use trivalent neodymium as a paradigm. This is appropriate since (a) most of the physical phenomena relevant to rare-earth lasers are present in Nd and (b) Nd is the most extensively used rare earth for lasers and has been lased in all forms of condensed matter - crystals, glasses. 

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