Laser-induced fluorescence and generation in laser plasma

LEV NAGLI, Physics Department, Ariel University, Ariel, Israel, Petah Tikva, Israel (levna@ariel.ac.il)

LIBS diagnostics employ LIP emission spectra, which display emission lines of the targeted elements. The improvement of the LIBS is the laser-induced luminescence of atoms (LIBS-ALIF) [1] and molecules (LIBS-MLIF) [2] under appropriate laser excitation in laser-induced plasma(LIP). The next step in the LIBS development is finding the lasing effect in a laser-induced plasma under strong pumping at resonant transitions of atoms in LIP. Lasing occurs in ambient atmosphere and is characterized by strong spectral intensity, low divergence, and, in many cases, strong polarization.  We nominate this effect as Laser-Induced Plasma Lasers (LIPL).

Several types of LIPLs were investigated. The three-level and four-level generations are characterized by the generations from the upper generation level E_u, which is inversely populated from the pumped level E_p through fast electron impact transitions.

The present talk explores the differences between the E_u population in ALIF and LIPL.

Fig.1 presents examples of Ti ALIF(a), Ti LIPL(b) spectra under excitation at 228.0 nm, and the transition scheme (c).

Fig 1. (a) and (b) are Ti LIF and LIPL spectra under excitation at 228.0 nm, respectively. Red numbers indicate the wavelengths at which generation is found. (c) Transition schemes: black upward-pointing arrows represent excitation transitions. Violet curved arrows indicate collisional transitions. Dashed black arrows pointing downward represent spontaneous transitions, while red dashed arrows indicate generation transitions. The numbers along the arrows correspond to the pumping and generation wavelengths.

[1] R. M. Measures and H. S. Kwong,  TABLASER: trace (element) analyzer based on laser ablation and selectively excited radiation, Appl. Opt. 18 (1979) 281-285• doi: 10.1364/AO.18.000281

[2] L. Nagli, M. Gaft, Combining Laser-Induced Breakdown Spectroscopy with Molecular Laser-Induced Fluorescence, App. Spectroscopy, 70 (2016)  585–592.  DOI: 10.1177/0003702816631292Enter the body of your abstract here