Infrared-microwave two-photon spectroscopy: Theν2band of NH3

Abstract

A spectroscopic method is developed in which the frequency of microwave radiation is added to or subtracted from that of infrared radiation by using two-photon processes in molecules. By utilizing many lines of the CO2 and N, O lasers, this method enables us to perform systematic high-resolution spectroscopy in the 1O-JLf,m region. Both straightforward two-photon absorption spectroscopy and two-photon Lamb-dip spectroscopy can be used. We describe the theory of this method and its application to the observation of the v, band of "NH, and "NH3. 132178

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

“…The operator code for this interaction is 600VV in the SPFIT/ SPCAT programs A total of 4394 transitions were included in the current analysis, including 2166 transitions assigned in this study and 2228 transitions from previous microwave studies 16,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] and infrared studies. [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] Each of the 4394 transitions was weighed by its experimental uncertainty. The details for all previously available transitions are available in Ref.…”

Double Resonance Sub-Doppler Study of the Allowed and ΔK = −3ForbiddenQ(3, 3)Transitions to the ν2Vibrational State of14NH3

“…It should be noted that the molecular field gradient parameter q 02 in Eq. [7] is a linear combination of the tensor components q 02 ϭ (q zz Ϫ q yy )/ 2 Ϫ iq xy and it is obviously different from (q) in Eqs. [3] and [5].…”

“…The vibration-rotation transitions to the lowest fundamental vibrational level of 14 NH 3 have been the subject of numerous studies (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Some of them provide a detailed analysis of the 2 band (12)(13)(14)(15); other works are focused to one or several transitions which are studied by a special experimental technique sometimes even with resolved hyperfine structures using a sub-Doppler resolution (11, 16 -19).…”

“…Ammonia was also the first polyatomic molecule observed in the interstellar space (5) and is a well-known gas constituent in the atmospheres of the giant planets Jupiter and Saturn (6). Ammonia has played an important role in the introducing of many new experimental laser techniques in spectroscopy, e.g., MW-IR double resonance (7)(8)(9), laser Start (9,10), two photon spectroscopy (10), or laser sideband spectroscopy (11).…”

Frequency Tunable Laser Sources.

“…16 pm line was encountered becau se of the lack of a good fi lt er to discriminate t h e pump and Li-ic e m i s s i o n ' , -i velengths. Ti-ic transmission of ti-me filter was measured to be on t h e or d e r at .1% at 10.286 pm a n d a b o u t 3% at 11.46 t a .…”