Jacques Lukasik

Vibrational relaxation of ortho and para-H2 in the range 400-50 K

Abstract The vibrational relaxation of ortho-para-H 2 mixtures was studied in the interval 400-50 K. At and above 300 K the ortho and para self-relaxation rates, k oo and k pp , are identical within experimental error. In the low temperature range, k oo > k pp and k oo is found to vary slowly with temperature.

Experimental study of the vibrational relaxation of ortho and para-H2 in collisions with 4He in the range 300–50 K

Abstract The vibrational relaxation of ortho-para-H 2 in collisions with 4 He has been studied in the interval 300–50 K. At 300 K the ortho H 2 - He and para H 2 - He rates are identical within experimental error. In the low temperature range .

Tunable, millijoule radiation extending to the 16 μm region

Abstract Efficient Stimulated Raman Scattering (SRS) in liquid nitrogen between 15 and 18 μm was obtained. Infrared radiation output was continuously tunable and narrow-band with energies up to 1.7 mJ.

Tunable coherent vacuum ultraviolet generation in carbon monoxide in the 1150 Å range

Abstract Coherent and tunable over 500 cm-1 radiation in the vacuum ultraviolet (VUV) in the 1150 A region has been generated by resonantly enhanced 4-wave sum frequency mixing in carbon monoxide. Theoretical estimates of the third-order nonlinear susceptibility are shown to be in reasonable agreement with the observed conversion efficiency in CO.

Molecular gases as a source of coherent, tunable XUV radiation

Abstract Coherent and broadly tunable over 3500 cm -1 extreme ultraviolet (XUV) radiation from 935 to 967 A has been generated by frequency tripling the second harmonic output of a rhodamine 590 pulsed dye laser in molecular nitrogen and carbon monoxide. The scheme exploits high lying Rydberg and valence states of these gases and leads to the production of about 5 × 10 9 XUV photons per pulse corresponding to a conversion efficiency of 5 × 10 -6 .

Vibrational relaxation of D2 in collisions with He in the range 400—80 K

Abstract The vibrational relaxation on n -D 2 in collisions with 4 He has been studied in the interval 400—80 K. The experimental values are compared with recent theoretical calculations by Alexander.

Vacuum ultraviolet generation in phase matched carbon monoxide

Abstract Resonantly enhanced four-wave sum frequency mixing in phase matched carbon monoxide leads to the generation of continuously tunable over 1200 cm -1 coherent VUV radiation in the 1150 A range. Experiments allow to determine the VUV absorption cross sections and indices of refraction of CO. Multiphoton photolysis of CO has been observed and confirmed by the VUV absorption in atomic carbon.

Observation of stimulated Raman scattering between υ = 1 and υ = 2 levels in hydrogen gas

Abstract The first observation of the stimulated Raman effect in hydrogen gas where scattering originates in the excited υ = 1 level and leads to a considerable increase of population in υ = 2 is reported.

Laser induced processes in highly excited states in molecules

Multiphoton excitation techniques are used to demonstrate laser induced processes involving high energy (E≳11ev) electronic states in such molecular gases as nitrogen or carbon monoxide. The method utilizes high power, tunable dye lasers and produces vacuum ultra‐violet radiations through direct multiphoton excitation, laser assisted collisional processes or nonlinear optical effects such as sum‐frequency mixing.

Vacuum-ultraviolet emissions from laser-excited b ′ 1 ∑u+ state of molecular nitrogen

Selective excitation of the b′1∑u+ valence state of molecular nitrogen using a single laser source is described. The excitation process utilizes a two-photon transition to the intermediate a1Πg state followed by a single-photon transition to the target state. The excitation is confirmed by observation of the VUV emission from the b′ state to high-vibrational levels of the ground molecular state. The b′-state population of N2 is estimated to be greater than 1013 cm−3. Generation of highly excited atomic nitrogen following the two-photon excitation of the a1Πg molecular state is reported.