Diode Laser Spectroscopy of Van Der Waals Complex Molecule

对弱结合分子的详细研究是重要的，因为从这种复合物的光谱学中可以定性地了解分子间长程作用力的性质。傅里叶变换微波光谱结合脉冲喷嘴技术对弱键合分子进行了广泛的研究。除了微波波段的转动光谱外，高分辨红外光谱研究分子复合物也具有重要意义，因为它可以直接了解弱键的动力学性质，如振动预解离和大幅度运动等.在本研究中，我们发展了中红外半导体激光光谱，用于检测弱键分子复合物，例如货车范德华络合物和氢键络合物。利用脉冲喷嘴技术在超声速自由膨胀射流中生成了弱结合的配合物，并对配合物的红外吸收光谱进行了研究。 ...更多信息 直接观察。半导体激光器发出的可调谐红外辐射经准直后进入高真空分子束室，激光通过两个近似平行的反射镜近似垂直于分子束穿过分子束约10次。通过由buster泵和旋转泵支持的6英寸扩散泵对腔室进行评价。吸收信号经锁相放大器处理后，用矩形波平均器检测，并在微机中累加，用本仪器测量了CO分子的红外基频，得到了超声速自由膨胀射流中CO分子的转动温度低至3 K，（N_2O）_2二聚体的红外吸收光谱在1270 cm ~ <-1>2区，对应于nu_1带（N-O伸缩）的单体，然后测量和分子束的特征与使用的光谱进行了详细的检查。我们在2200 cm ~ 2的频率范围内测定了新的货车范德华络合物OCS-HCl和OCS-N_2 O，<-1>并对其进行了归属，同时研制了检测弱键合络合物的二极管激光微波双共振光谱仪。双共振法对于配合物的检测具有一定的优势，如检测到分子配合物的双共振信号，红外光谱的归属就变得明确。并对双谐振系统进行了初步的实验研究。少

Detailed studies of weakly bounded molecules are important because the qualitative knowledge about the nature of long range intermolecular forces can be obtained from the spectroscopy of such complexes. The weakly bounded molecules have been studied extensively by Fourier transform microwave spectroscopy combined with pulsed nozzle technique. In addition to rotational spectroscopy in the microwave region, the high resolution infrared studies of the molecular complexes are of great interest because the dynamical properties of the weakly bounded bond such as vibrational predissociation and large amplitude motion can be known directly.In the present study, we developed mid-infrared diode laser spectroscopy for the detection of weakly bounded molecular complexes, such as van der Waals complexes and hydrogen bonded complexes. The weakly bounded complexes were generated in the supersonic free expansion jet using pulsed-nozzle technique, and the infrared absorption spectrum of the complexes w … More ere observed directly. Tunable infrared radiation from a diode laser source was collimated and passed into a high vacuum molecular beam chamber.The laser light traversed the molecular beam approximately perpendicularly to the beam about ten times by means of two near-parallel mirrors. The chamber was evaluated by a 6-inch diffusion pump backed up by a buster pump and a rotary pump. The absorption signal was processed by a lock-in amplifier and detected by a boxcar averager and then accumulated in a micro-computer.Using the present instrument, the fundamental infrared band of CO molecule was measured and the rotational temperature of CO molecule in the supersonic free expansion jet was found to be low as 3 K, which was low enough to produce van der Waals complexes.The infrared absorption spectrum of (N_2O)_2 dimmer in the 1270 cm^<-1> region, which corresponded to the nu_1 band (N-O stretching) of monomer, was then measured and the characteristic features of the molecular beam was examined in detail with use of the spectrum. New van der Waals complexes such as OCS-HCI and OCS-N_2O were measured in the frequency range of 2200 cm^<-1> and we are now making their assignments.The diode laser microwave double resonance spectrometer for the detection of the weakly bounded complexes was also developed. The double resonance method has advantages for the detection of the complexes, for example, the assignments of the infrared spectrum becomes definite if a double resonance signal of the molecular complexes is detected. We also made the preliminary test of the double resonance system. Less