Plasma ignition threshold disparity between silver nanoparticle-based target and bulk silver target at different laser wavelengths

Abstract

Plasma ignition threshold of nanoparticle-based and bulk silver targets was measured in air. The plasma was initiated by a Nd:YAG laser at wavelengths of 355, 532, and 1064 nm. The plasma ignition was monitored utilizing the prominent Ag I line at 546.5 nm. Lower ignition thresholds of the nanoparticle-based silver target were estimated at 0.4±0.02, 0.34±0.04, and 0.27±0.035 J cm −2 coupled with the different laser wavelengths, respectively. In contrast, the bulk silver target plasma exhibited an order of magnitude higher ignition threshold. A three orders of magnitude enhanced emission intensity from the nano-based target over the bulk target was achieved at lower levels of laser irradiation. A reduction of the thermal diffusion length of the nanosilver was assumed in order to theoretically predict this reduction in the plasma threshold. In addition, the effect of self-reversal on the resonance lines was taken into consideration.

Feasibility of Using Boltzmann Plots to Evaluate the Stark Broadening Parameters of Cu(I) Lines

“…This factor tends to be larger than zero and equal to one in the limit of purely optically thin line. 9,[12][13][14] This coefficient is given by the following expression…”

“…The experimental setup has been described in detail in previous publications. 9,[12][13][14] It comprises a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser at a wavelength of 532 nm, pulse duration from 5 ns, and 100 AE 5 mJ output pulse energy. The plasma is created at the surface of flat a copper target (99.99% purity; K.J.…”

“…[1][2][3][4][5][6][7][8][9][10] The natural process of plasma self-absorption effectively leads to distortion of emission line shape and consequently over and/or underestimated of plasma parameters. [9][10][11][12][13][14] However, the distorted lines can be recovered after carrying well-known procedures utilizing the presence of the optically thin H a line. [9][10][11][12][13][14] The Boltzmann plot method has been previously used to estimate the missing values of transition probabilities and Stark broadening parameters of several atomic transitions.…”

“…[9][10][11][12][13][14] However, the distorted lines can be recovered after carrying well-known procedures utilizing the presence of the optically thin H a line. [9][10][11][12][13][14] The Boltzmann plot method has been previously used to estimate the missing values of transition probabilities and Stark broadening parameters of several atomic transitions. 10,[15][16][17][18][19][20][21][22][23][24][25] This should be ultimately carried out provided that at least one of these quantities should be available with sufficient accuracy.…”

Opacity Corrections for Resonance Silver Lines in Nano-Material Laser-Induced Plasma

“…However, strong enhanced plasma emission was noticed when focusing laser radiation onto targets made of pure nanomaterials [12][13][14]. This enhanced emission was related to the sudden increase of the population density of the ground state atoms in the same ratio of the amount of enhanced emission I λ0 nano /I λ0 bulk ≈ N λ0 nano /N λ0 bulk [12][13][14], i.e., more of cold atoms, N 0 nano , exist at the outer peripheries of plasma produced from nanomaterials [14], but without further increase in the plasma excitation temperature [2]. This enhanced emission enables the spectral line intensity I λ0 Nano of the resonance lines to exceed the corresponding, upper-limit black body radiation intensity I λ0 Nano ≥ B(λ 0 ,T ex ), B(λ 0 , T ex ) = 2hc 2…”