Laser isotope separation and the multiphoton decompotions of formaldehyde using a focused DF laser: the effect of single- or multi-line irradiation

✍ Scribed by D.K. Evans; Robert D. McAlpine; F.K. McClusky

• Publisher: Elsevier Science
• Year: 1979
• Tongue: English
• Weight: 361 KB
• Volume: 65
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(79)87054-2

✦ Synopsis

The dewmposition of molecules subjected to intense pulsed infrared radiation has been a subject of =onsidembie interest recent& [ 1 ,?I_ For I number of polyrtomic moIecuIes, SF6 principal among them, cothrionless dervmposit ion processes in IR fields of I-50 JfLm' have been clezrly demonstrated [3,-l]_ Two triatomic molecuks, 13~ and OCS, have been reported to undergo coIlisionI+ss muttiphoton deanuposition (MPD), though in these cases laser fields > 50 Jjcm~ are required [5 j _ Current coltisionkss models [ I,3f of MPD view the multiphoton absorption (AlPA) as occurring through three distinct energy regions of the excited moIecuIe_ For the lowvest of these regions (II;), rcsonrtnces be-tr\cen the (usually fixed-frequency) photon fieId and particular moIecuIar transitions are required_ A large anharmonicity of the mode in!thIIy pumped (as is the case for the HF Iasser induced MPD of formic acid [6] and methanol [7 1) will have the effect of quickly shifting sequenri31 esckirions in this mode out of resonance N-ith the photon field. When this occurs, the molecuIe must either (I) be pumped through arbitrary rransirions (if such esist) which are accidentaliy degenerate with the laser kid, (3) undergo simultaneous multiphoton transitions or (3) require an IR field of sufficient intensity to overcome the anharmonic shift by broadening the pumped Ievek All of these possibil-_ ities ace expected to be less efficient than sequential