摘要
3d过渡金属化合物的光谱研究在天文物理,表面科学等领域有重要的意义。3d过渡金属化合物的构型和成键特性也是物理化学研究中非常关注的问题。本论文主要研究3d过渡金属Co和Ni的氢化物和氧化物的激光诱导荧光(LIF)光谱。我们采用脉冲直流放电和超声射流相结合的方法产生CoO,CoH和NiH的瞬态分子,利用激光诱导荧光技术,研究了这3种分子在若干波长范围内的激发光谱,并测量了每种分子不同上电子态在无碰撞条件下的寿命。对每个谱带都做了振转分析,拟和得到了光谱常数,讨论了相应分子的结构和成键问题。取得以下的主要研究成果:
·CoO分子的激光诱导荧光激发谱。
利用Co电极放电溅射出的Co原子与和O_2/Ar混合气体反应产生CoO分子,研究了超声射流条件下CoO在540-725 nm范围的激光诱导荧光(LIF)激发谱,并测量了大部分的谱带上能级无碰撞条件下的寿命。在光谱中共观测到了95个谱带,其中59个是新发现的谱带。通过对谱带的振转分析,并结合上电子态的寿命信息,标识了3个Ω=7/2-7/2跃迁带系,C~4△_(7/3)-X~4△_(7/2),E~4△_(7/2)-X~4△_(7/2)和F~4△_(7/2)-X~4△_(7/2),其(0,0)带分别位于13950cm~(-1),15241cm~(-1)和15650cm~(-1);一个Ω=9/2-7/2的跃迁带系标识为D~4φ_(7/2)-X~4△_(7/2),其(0,0)带位于14609cm~(-1)。在所观测到的59个新谱带中,标识了三个Ω'=5/2-X~4△_(7/2)的垂直跃迁带系,[13.99]Ω'=5/2-X~4△_(7/2)(v'=0-6-v"=0),[14.20]Ω'=5/2-X~4△_(7/2)(v'=0-6-v"=0)和[15.85]Ω'=5/2一X~4△_(7/2)(v'=0-4-v"=0),(O,0)带分别位于13998cm~(-1),14202cm~(-1)和15858cm~(-1)。并讨论了这3个带系上电子激发态可能的电子组态和构型。
·CoH分子的激光诱导荧光激发谱。
利用利用Co电极放电溅射出的Co原子与CH_3OH蒸汽反应产生CoH分子,研究了CoH在530nm—730nm波长范围内的激光诱导荧光激发谱,观测到了的9个跃迁谱带,其中3个谱带是新发现的。通过对谱带结构的振转分析,结合上电子态的寿命信息对光谱进行了标识,其中5个位于13794cm~(-1),15136cm~(-1),16372cm~(-1),17477cm~(-1)和18430cm~(-1)的Ω'=4-Ω"=4谱带组成的振动序列归属到A' ~3φ_4-X ~3φ_4(v'=1-5-v"=0)跃迁,位于16002cm~(-1)的谱带确认为是Ω'=3—Ω"=4的跃迁,位于14073cm~(-1),15402cm~(-1)和17678 cm~(-1)的3个新观测到的Ω'=3—Ω"=4谱带被归属到一个新的跃迁D ~3△_3-X ~3φ_4(v'=1,2,4-v"=0),振动频率约为1582 cm~(-1),与理论计算的D态的能量和振动频率等分子常数值基本相符。此外,还对CoH,CoF和Co~+低激发态的光谱做了类比和讨论。
·NiH分子的激光诱导荧光激发谱。
利用Ni电极脉冲直流放电产生的Ni原子与CH_3OH蒸汽反应产生NiH分子,研究了NiH在超声射流条件的LIF激发谱,对15000-22000 cm~(-1)的30个谱带进行了转动分析,结合谱带上电子态的寿命信息。标识了基态X ~2△_(5/2)(v"=0)到A,B,D,E,F,G和I电子态的7个跃迁带系,其(0,0)带依次位于15527cm~(-1),15990cm~(-1),16158cm~(-1),16345cm~(-1),17100cm~(-1),18437cm~(-1)和17317cm~(-1)。得到这些电子态较为完整的包括精确的振动频率,非谐性系数,转动常数,平衡核间距等分子常数,首次报道了NiH19000-22000 cm~(-1)的光谱,在此范围内观测到了很多电子态的高振动能级,发现了一些新谱带。
The spectroscopic characterizations of transition metal containing compounds play important role in various practical applications such as astrophysics,high tempera-ture chemistry and surface science.In addition,the study of structure and bonding properties of transition metal containing compounds provides important data for the understanding of fundamental chemical reaction processes.This thesis presents the ex-perimental studies on the laser-induced fluorescence(LIF)excitation spectra of the three 3d transition-metal Co and Ni hydride and oxide.The CoO,CoH and NiH molecules were produced by reaction of sputtered metal atoms with small molecule gas under su-personic jet cooled condition.Every band observed has been rotationally analyzed.The electronic structure and chemical bonding of each molecule was discussed.The main results are summarized as follows:
●The laser-induced fluorescence excitation spectrum of jet-cooled CoO molecules has been reinvestigated in the range of 540-725nm.A to-tal of 95 bands have been observed,among them,59 bands were reported for the first time.Three vibrational band progressions were assigned as C~4△_(7/2)-X~4△_(7/2),E~4△_(7/2)-X~4△_(7/2)and F~4△_(7/2)-X~4△_(7/2),with (0,0)band at 13950cm~(-1),15241cm~(-1)and 15650cm~(-1),respectively. AnΩ=9/2-7/2 transition system with(0,0)band at 14609cm~(-1)was assigned as D~4Φ_(7/2)-X~△_(7/2).NineteenΩ'=5/2-Ω"=7/2 vertical transi-tion bands have been classified into three transitions with(0,0)band at 13998,14202 and 15858 cm~(-1),designated as[13.99]Ω'=5/2-X~4△_(7/2), [14.20]Ω'=5/2-X~4△_(7/2)and[15.85]Ω'=5/2-X~4△_(7/2),respectively. The possible electronic configurations of the three upper states have been discussed.
●The laser induced fluorescence excitation spectrum of CoH molecule has been investigated in the range of 530-730nm.A total of 9 bands have been observed,and three new bands were reported.Lifetime measurements for the upper states of all the bands were carried out under the collision-free condition.Accurate rotational constants of every band have been obtained by least-square fitting.FiveΩ'=4-Ω"=4 strong bands were designated as A' ~3Φ_4-X ~3Φ_4(v'=1-5-v"=0) transition.Band at 16002 cm~(-1)was proved to beΩ'=3-Ω"=4 transi-tion.The three new bands at 14073cm~(-1),15402cm~(-1)and 17678 cm~(-1) were proved to beΩ'=3-Ω"=4 transition,designated as D ~3△_3-X ~3Φ_4(v'=1,2,4-v"=0)electronic transition.Accurate rotational con-stants of these bands have been obtained.The spectroscopic constants are compared with the isovalent CoF molecule and Co~+ ion.
●The laser-induced fluorescence excitation spectra of supersonic jet-cooled NiH have been recorded in the range of 15000-22000 cm~(-1),in which the NiH molecules were produced by the reaction of sputtered nickel atoms with methanol.Thirty NiH bands were rotationally an-alyzed and classified into six electronic transitions,A,B,D,E,F and G state from the X~2△_(5/2)(v"=0)ground state.The molecular pa-rameter such as vibrational frequency,unharmonic constant,rota-tional constant and equilibrium length of these states have been deter-mined.The 19000-22000 cm~(-1)spectrum of NiH was reported for the first time.In addition,a few weak bands were also observed,and the lifetimes of the upper states involved in these bands were measured.
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