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In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity property of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A 2 R þ ð ¼ 0; 1Þ ! X 2 PðD ¼ 0Þ at 308 nm and A 2 R þ ð ¼ 0; 1Þ ! X 2 PðD ¼ 1Þ at 287 nm, O I transitions 3p 5 P!3s 5 S 0 at 777.41 nm, and 3p 3 P!3s 3 S 0 at 844.6 nm, N 2 (C-B) second positive system with electronic transition C 3 P u ! B 3 P g in the range of 300-450 nm and N 2 þ (B-X) first negative system with electronic transition B 2 R þ u ! X 2 R þ g ðD ¼ 0Þ at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p 3 P 0 !2s 3 S at 388.8 nm, 3p 1 P 0 ! 2s 1 S at 501.6 nm, 3d 3 D!2p 3 P 0 at 587.6 nm, 3d 1 D!2p 1 P 0 at 667.8 nm, 3s 3 S 1 !2p 3 P 0 at 706.5 nm, 3s 1 S 0 !2p 1 P 0 at 728.1 nm, and H a transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 6 25 K and 340 6 25 K and it increases to 320 6 25 K and 360 6 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture, respectively. Additionally, the vibrational temperatures range from 2200 6 100 K and 2500 6 100 K for pure helium and helium/oxygen (0.1%) mixture, respectively. The plasma jet was tested on heat sensitive polymer films used in biomedical applications such as polyethylene terephthalate and poly-L-lactide samples continuously for several minutes without causing any physical or thermal damage to the films. The plasma jet produces significant reactive species of interest while the gas temperatures remain very low demonstrating its potential for a range of biomedical applications. V C 2013 AIP Publishing LLC. [http://dx.

We present measurements and analysis of laser induced plasma neutral densities and temperatures in dry air by focusing 200 mJ, 10 MW high power, 193 nm ultraviolet ArF ͑argon fluoride͒ laser radiation to a 30 m radius spot size. We examine these properties that result from multiphoton and collisional cascade processes for pressures ranging from 40 Torr to 5 atm. A laser shadowgraphy diagnostic technique is used to obtain the plasma electron temperature just after the shock front and this is compared with optical emission spectroscopic measurements of nitrogen rotational and vibrational temperatures. Two-color laser interferometry is employed to measure time resolved spatial electron and neutral density decay in initial local thermodynamic equilibrium ͑LTE͒ and non-LTE conditions. The radiating species and thermodynamic characteristics of the plasma are analyzed by means of optical emission spectroscopy ͑OES͒ supported by SPECAIR, a special OES program for air constituent plasmas. Core plasma rotational and vibrational temperatures are obtained from the emission spectra from the N 2 C-B͑2+͒ transitions by matching the experimental spectrum results with the SPECAIR simulation results and the results are compared with the electron temperature just behind the shock wave. The plasma density decay measurements are compared with a simplified electron density decay model that illustrates the dominant three-and two-body recombination terms with good correlation.

Cold atmospheric plasma (CAP), an ambient temperature ionized gas, is gaining extensive interest as a promising addition to anti-tumor therapy primarily due to the ability to generate and control delivery of electrons, ions, excited molecules, UV photons, and reactive species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) to a specific site. The heterogeneous composition of CAP offers the opportunity to mediate several signaling pathways that regulate tumor cells. Consequently, the array of CAP generated products has limited the identification of the mechanisms of action on tumor cells. The aim of this work is to assess the cell death response of human myeloid leukemia cells by remote exposure to CAP generated RNS by utilizing a novel resistive barrier discharge system that primarily produces RNS. The effect of variable treatments of CAP generated RNS was tested in THP-1 cell (human monocytic leukemia cell line), a model for hematological malignancy. The number of viable cells was evaluated with erythrosine-B staining, while apoptosis and necrosis was assessed by endonuclease cleavage observed by agarose gel electrophoresis and detection of cells with the exclusionary dye propidium iodide and fluorescently labeled annexin-V by flow cytometry and fluorescent microscopy. Our observations indicate that treatment dosage levels of 45 s of exposure to CAP emitted RNS-induced apoptotic cell death and for higher dosage conditions of ≥50 s of exposure to CAP induced necrosis. Overall the results suggest that CAP emitted RNS play a significant role in the anti-tumor potential of CAP.