University of Arizona, Dept. of Physics Molecular Spectroscopy of Rotational, Vibrational, and Electronic oscillations Abram Young University of Arizona, Dept. of Physics J2,0 ← 1,0 Transition

Generation of THz waves by Optical Rectification

Reference pulse Pulse through sample Discrete Fourier Transform to recover spectrum and phase

THz signal through NH3 cell 11 cm cell with thin Mylar windows Evacuated to <50 mTorr before each scan Adjustable pressure 0.1 – 100 Torr 0.119 pSec shift from vacuum sample approximates index of refraction NH3 Rotational transitions Noise floor

Low Order Rotational Lines J1,0 ←0,0 = 0.572 THz (0.597 THz) J2,0 ←1,0 = 1.215THz (1.193 THz) J3,0 ←2,0 = 1.765THz (1.790 THz)

Future Measurements For room temperature Ammonia, Sub-Doppler Lamb dip spectroscopy Greatly reduced from atomic spectra due to greater reduced mass and lower oscillation frequency For room temperature Ammonia, ~1.8 MHz for J1<-0 (3.6 MHz, 5 MHz for J2<-1 and J3<-2)

5 Bands from 140GHz-900GHz Microlambda 10-20 GHz multilock Synth Signal conditioning DC supplies 5 Bands from 140GHz-900GHz Microlambda 10-20 GHz multilock Synth Electronically Chopped Amplifier Varying multiplication bands Rx Tx sample