Gaseous Ion Lasers

20 eV above the ionic 3p ground state. In Fig. 8.16 a partial level scheme for Ar is given, with laser hnes connecting 3p 4p levels and 3p 4s levels indicated. Several blue and green laser lines are obtained (5145, 5017, 4965, 4880, 4765, 4727, 4658, 4579 and 4545 A). The strongest lines are 

Energy level diagram of the Ar ion, with argorr-ion laser Mnes indicated 

At very high discharge currents laser transitions are also obtained in doubly ionized argon. Several UV lines in the wavelength region 300—386 nm are then obtained with a total power up to 5W. 

The krypton-ion laser has the same construction as the argon-ion laser but the discharge tube is instead filled with krypton. Apart from blue and green lines, several red lines are also obtained with this laser (7931, 7525, 6764, 6471, 5682, 5309, 5208, 4825, 4762, 4680, 4131 and 4067 A), as well as strong UV lines (3564, 3507 and 3375 A). Ion lasers arc discussed in gi eater detail in [8.57]. 

When using laser mirrors with a high reflectivity in the blue-green region all the lines are produced simultaneously. Argon-ion lasers with a total output power of up to 30 W are commercially available. In Fig.8.17 the 

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C.C. Davis, T.A, King Gaseous ion lasers. In Advances in Quantum Electronics, ed. by D.W. Goodwin (Academic Press, London 1975)... 

CC Davis, TA Davis. Gaseous ion lasers. In DW Goodwin, ed. Advances in Quantum Electronics. London Academic Press, vol. 3, 1975. 

Laser is an acronym for light amplification by simulated emission of radiation. In SERS, as well as in other types of Raman scattering experiments, a continuous-wave (CW) gaseous ion laser is normally used, e.g., an argon-or krypton-ion laser. It is also possible to use a pulsed laser, such as a neodymium, Nd ", in yttrium-aluminum garnet (YAG) laser however, a much... 

The rates of these reactions bodr in the gas phase and on the condensed phase are usually increased as the temperature of die process is increased, but a substantially greater effect on the rate cati often be achieved when the reactants are adsorbed on die surface of a solid, or if intense beams of radiation of suitable wavelength and particles, such as electrons and gaseous ions with sufficient kinetic energies, can be used to bring about molecular decomposition. It follows drat the development of lasers and plasmas has considerably increased die scope and utility of drese thermochemical processes. These topics will be considered in the later chapters. 

Watson, C.H. Baykut, G. Eyler, J.R. Laser Photodissociation of Gaseous Ions Formed by Laser Desorption. Anal. Chem. 1987,59, 1133-1138. 

Both the pulsed and cw lasers were used for photodissociation of gaseous ions produced by laser desorption. The cw laser had a maximum output power of 50 watts at 10.61 micrometers and a beam diameter of 6 mm. The pulsed laser produced 2.6 joules in a pulse of 1 microsecond duration at 10.61 micrometers and had a 2 x 3 cm rectangular beam shape. Modifications of the FTICR vacuum chamber that facilitate ion irradiation have been reported previously (13). 

Use of a single laser for desorptlon/dissociation. Photodissociation of small gaseous ions using a pulsed C02 laser has been reported (15), so an attempt was made both to form ions and to photodissociate them with sequential laser pulses from the same pulsed laser using the irradiation scheme shown in Figure 1. As... 

Laser desorption (LD) is an efficient method for producing gaseous ions. Generally, laser pulses yielding from 106 to 1010 W cm 2 are focused on a sample surface of about 10 3-l() 4cm2, most often a solid. These laser pulses ablate material from the surface, and create a microplasma of ions and neutral molecules which may react among themselves in the dense vapour phase near the sample surface. The laser pulse realizes both the vaporization and the ionization of the sample. 

Mass spectrometry and gas-phase ion chemistry of phenols concerns this class of compounds and, in particular, the various types of gaseous ions formed from them, as objects of fundamental interest and analytical signihcance. However, in the special case of phenols, a mass spectrometry with phenols has been developed. As mentioned in the Introduction, one of the modern methodologies for the formation of ions from polar and/or high-molecular mass, and thus non-volatile, organic and bioorganic compounds, relies on the use of various phenolic compounds as matrices for ion generation. Matrix-assisted laser ionization/desorption has become one of the major essential ioniza-... 

Fig. 6.15 Resonance Raman spectrum of gaseous iodine. Argon ion laser line at 2 = 514.5 nm was used for the excitation.

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