Rotational laser emission by HF has been observed at 33 frequencies between 325 and 1250 cmminus;1from the flash photolysis (1.2 mgr;sec FWHM) of vinyl fluoride and of 1,1hyphen;difluorethylene. The transitions lie within thev= 0 tov= 5 manifolds and range fromJPrime;rarr;Jprime;= 8rarr;7 to 31rarr;30. Increasing the atomic weight or the partial pressure of the inert buffer gas (He, Ne, or Ar) raises the gain of nearly all transitions, showing that collisional relaxation processes are active in pumping the laser emission. The high gains displayed by both precursors in theJ= 14rarr;13 transitions for thev= 0,1,2, and 3 manifolds indicate thatVrarr;Renergy transfer is pumping molecules into thevprime;,J= 14 state from the nearhyphen;resonantvprime;+1,J= 2, 3, and 4 states. In a similar way, the highestJtransitionsJ= 31rarr;30 to 28rarr;27 withv= 0 and/or 1, are best explained byVrarr;Renergy transfer from nearhyphen;resonant lowhyphen;Jstates from much higher vibrational manifoldsvprime;= 4, 5, and 6. This would imply collisionhyphen;induced multiquantum energy transfer with large Dgr;v(up to Dgr;v= 5) and large Dgr;J(up to Dgr;J= 26) or a rapid succession of steps with smaller Dgr;vand Dgr;J. In contrast, the high gains displayed by theJ= 10rarr;9 transitions in thev= 0, 1, and 2 manifolds are best explained in terms ofRrarr;Trelaxation from a uniform nascent population. While there are indications that the nascent rotational distributions provided by these photoeliminations probably furnish population to highJstates, the gain patterns indicate that theVrarr;RandRrarr;Tenergy relaxation processes are strongly influential, the former surely involving multiquantum steps with large Dgr;Jand probably with Dgr;v1 as well.
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